Qweak GEM installation log book

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Detector installation

The Qweak GEM detector has been installed in the doghouce in Hall-C and the HV was turned on. On the scope picture below is shown the GEM trigger out pulse, after it has been amplified and integrated with timing filter amplifier. The high voltage supply is placed in the doghouse with the other electronics.




We have the NIM Bin with the following modules: Leading edge discriminator, timing filter amplifier(X2), Gumstix module.


The gas bottle filled with ArCO2 is placed outside the doghouse. We have two 90 ft shielded twisted ribbon cables next to region 1 area.

cables need to be routed about colimator 2.



R1 HallC Bubbler 7-27-10.jpg


Met with Kelly Tremblay to discuss survey plans. Goal is to be ready for Qweak collaborators and survey crew to align detector on June 4. The "Fork" used to connect the GEM detector to the translator will be fiducialized for the laser survey system by mounting 4 targets on the fork. The request is to have the "Y" location surveyed in to 100 microns (this is essentially [math]\theta[/math]) . We desire the X-location to be surveyed within 250 microns. The Z - location beam upstream/downstream is the least critical.

DAQ computer name is : cdaql6

R1 ROC name : qwvme11 (

using the terminal server to login to the R1 ROC

telnet hctsv7 2006


telnet qwvme11

Gumstix and I2C

Brad Sawatzky: Contact for ordering gas ionfrastructure (bubbles, hose , valves,...)


Gumstix sees the network now. It will be known as qwgemgumstix and have the IP address

We may also use the terminal server to login via the Gumstix's serial port but you must be logged into cdaql6 (or a computer on the same network as cdaql6)

telnet hctsv11 2005

Runcontrol runs the cMsg server.

Gumstix contains cMsg client and subscribes to the Runcontrol cMsg server. once receiving message from ROC it then send out a message of the current thrshold value which the ROC has subscribed to . This tells the ROC to pulse again.

Carl Timmer has a sample code in C.

use Send and Get

ROC is a cMsg client as well

ROC spawns a task upon userGo and starts stepping through Discriminator setting task start a pulse and sleeps until a Mutext comes then it sends a cMsg to Gumstix

search jlab.org
[cdaq@cdaql6 ~]$ nslookup cdaqfs

Name:   cdaqfs.jlab.org

auto eth0
iface eth0 inet static

is go to the next threshold setting.

Location of Qweak coda DAQ files

Readout lists cdaq@cdaql6 ~/coda]$ ls ~/qweak/coda26/crl/

[cdaq@cdaql6 crl]$ codamaster

ROC libraries

ls ~/qweak/libraries/vme/v1495_gem/

Error message from V1495.

-> v1495ReadEvent()
0x1ad8900 (tShell): v1495ReadEvent: Error: header for word 3 from data packet != 0xE

qwvme11 boot parameters

The firmware is set for 32 MHz but it looks like the actual clock is 31 MHz.

boot device          : dc
unit number          : 0 
processor number     : 0 
host name            : cdaql6.jlab.org
file name            : /usr/local/coda/kern/5.5/vx2400_u1
inet on ethernet (e) :
host inet (h)        :
user (u)             : cdaq
flags (f)            : 0x20 
target name (tn)     : qwvme11
startup script (s)   : /home/cdaq/qweak/coda26/boot/qwvme11.boot


LV1 accept to V1495 has to have a gate width at least 1 MCLK cycle less than 3 MCLK cycles.

We used cdaql6 to write several coda data files the the V1495 reading out 1 detect.

at MCLK=16MHz we created the files

v1495_28.dat.0 and v1495_29.dat.0

Run 28 was short, run 29 was very long.

I saw the following CHIP IDs in the data file but the thresholds are so high there were no hits

Card=0  ChipID=0xa6c
i = 14 
Card=1  ChipID=0x8ec
i = 28 
Card=2  ChipID=0x8ec
i = 42 
Card=3  ChipID=0x6ec
i = 56 
Card=4  ChipID=0x0
i = 70 
Card=5  ChipID=0x66c

Its seems Card 4 is not getting its ID recorded but its I2C is responding. Perhaps a failed card? We loer MCLK to 8 MHz no change.



Two R1 detectors reside outside the Hall C doghouse. One detector was running in the doghouse and cosmic signals were observed which went away when turning the drift voltage down to equal the GEM preamplifier voltage (this is how we convince ourself that the signal is real without turning the detector completely off).

A data file was written using CODA v 2.6 installed on cdaql6 and the GW ROC. The MCLK signal however needed to be set to 16 MHz instead of 32 MHz. The V1495 was unable to "lock on " to the 32 MHz signal from the G0 clock. It is not understood why at this time. While sampling the data at 16 MHz is not a show stopper we will try to find a way to operate at 32 MHz. The same V1495 was able to lock onto our 32 MHz pulser at ISU without a problem.

A GEM detector was mounted on the rotator and was able to rotate 360 degrees freely. There was some concern that the Breakout board would hit a bolt coming up from the floor which secures the first collimator. There is at least a 3 inch gap between this bolt and the breakout board at the point of closest approach. A substantial amount of the bolt thread extends well beyond the nut. A request will be made to cut off the excess bolt that extends beyond the nut.


We are unable to record the VFAT output in the V1495 using the ribbon cables provided by JLab. The V1495 was no longer able to recorded the output of 3 VFAT cards when we switched from our 4 foot long, shielded, flat ribbon cables to JLab's 100 ft long rounded ribbon cables. We have seen this before. We had similar problems at ISU and found that they went away when a twisted pair FLAT ribbon cable was used. Signal integrity becomes important at the 40 MHz frequencies.

Path forward:

We will try to debug breakout board with VFAT electronics, the V1495, and two JLab shielded ribbon cables at ISU to determine if JLab's cables are not usable. We did successfully test the readout using 100 ft FLAT twisted pair cables during ISU beam tests. If the FLAT cables must be used then we will need to coordinate with Klaus on the cable holder to determine if the holder can accommodate flat cables or if we can use the rounded cables for the last [math]X[/math] meters of slack used by the cable holder.


R1 Nauvoo 6-13-10.jpg


R1 Nauvoo 7-29-10 RadTestVFAT.jpg R1 Nauvoo 7-29-10 RadTestVFAT Anoted.jpg


PRETRGe&EN1 scaler in Hall C counting house pannel port 6.

The Trig out of GEM A and B went into chanels 4 & 5 of the same scaler used for Alena's scintillator which records it values in the ROC file bank ID0x0403

Power strip control to reboot Hall C equipment can be accessed from the counting room computer


Check V1495

To check if the V1495 is installed I logged into the ROC from cdaql1

[cdaq@cdaql1 ~]$ telnet qwvme11

The V1495 address was set to 0811 so I changed it to 0933

Now I see that it is initializing

-> v1495Init(0x09330000)
0x1b09070 (tShell): v1495Init: v1495 Module has been successfully initialized.

0x1b09070 (tShell): v1495 module has been reset: 

value = 0 = 0x0

It seems I have the old I2C gumstix to Breakboard card and not the right RJ45 connector to allow me to talk I2C to the VFAT card (unless the VFAT card has gone bad). Effort to make my own cable according to Tamuna's pinout chart failed.



Paul and I were able to get CODA 2.6.1 to initialize the V1495 upon PRESTART. Apparently there is a problem running more than 1 DAQ at a time on different computers (perhaps they are trying to use the same rcServer?).


A GEM trigout signal is going upstairs to the scope. The timing amplifier downstairs is set to integrate the pulse over 100 ns. Is this why I see 600 ns Comsic pulses? I will check this with beam tomorrow morning.

I will use the discriminated output of HALO3 to determine if there is beam coming down the beamline and LUMI3 to determine if a target is in.

The HV for the above monitors may be observed through EPIC on cdaql6 with the following commands

  1. login to cdaql6
  2. ssh cvswrks@cdaql6
  3. /net/cdaqfs/home/EPICS/dvlepics/llapp/CaenHV/1-0/QWEAK/tk/hv.tcl

First Beam

I saw signals associated with an electron beam into Hall C for the first time today. The beam was being tuned and the detector was out of position so any signals were mostly background. The HV was -3600 Volts on the drift and -3300 Volts on the GEM preamplifier. The Trigout pulse was amplified in the doghouse by an Ortec timing amplifier set to integrate the signals over a 100 ns period.


GEM Timing Amp

The Ortec timing amplifier used to send the GEM output upstairs has an integrate time of 100 ns. The Phillips discriminator has a maximum output width of about 100 ns and we do see double pulsing sometimes so be careful. The max rate for a 50 ns GEM pulse is 20 MHz but the preamp width of 600 ns keeps us below 1 MHz, and the discriminator width of 100 ns keeps us below 10 MHz.

Qweak R1 DiscrTrigout 8-5-10 1.png Qweak R1 DiscrTrigout 8-5-10 2.png

With a 1 mil Aluminum target, the 10 MHz max rate may be at a beam current of 50 nA.

Add GEM scaler to MAP

login to cdaql4

cd $QWANALYSIS/Tracking/prminput/

The file


describes all the detectors used below are two relevant examples

 name = R1
 map = qweak_R1.map
 geom = qweak_new.geo
 name = TS
 map = qweak_trigscint_channel.map
 geom = qweak_new.geo
 mask = 0xffff

The scalers used for the GEM trigout pulse are plugged into the trigger scintillator scalers so I edited the file to look like this

! module.type  module.num  chan.num, det.type, det.name
  SIS3801, 0,  0, trigscint, ts2m_sca
  SIS3801, 0,  1, trigscint, ts2p_sca
  SIS3801, 0,  2, trigscint, ts1m_sca
  SIS3801, 0,  3, trigscint, ts1p_sca
  SIS3801, 0,  4, trigscint, GEMTrigOut_Naovoo_sca
  SIS3801, 0,  5, trigscint, GEMTrigOut_Urim_sca
  SIS3801, 0,  6, trigscint, ts2mt_sca
  SIS3801, 0,  7, trigscint, ts1mt_sca

The ROOT files are stored in


and named as QWEAK_runNumber.000.root

To reanalyze the tracking data without doing tracking go to the data directory

cd $QW_DATA/
 qwtracking -r 724 --QwTracking.disable-tracking

The Scaler is read out at fixed time intervals but those intervals can change depending on helicity flip rate and if a "fake" helicity flip rate is being used.

R1 Timing

Octant5 QweakScint R1Naovoo 8-6-10 Timing 1.png

200 px

200 px

200 px

200 px

R1 rate -vs- beam current

Run # Scint Naovoo


Took detector apart. GEM foils(all of them) are bunt. Some of the strips have discoloration, they have burnt spots.

The images below show all the GEM foils and PC board.


During the beam tuning at JLab, when all tracking chambers were in place, I saw the following on trigout with the detector off.

JLab Aug6 2010 BeamTune 10ma.jpg

Channel 3 (purple) is the trigout signal from the GEM detector. I believe Channel 2 was the Qweak scintillator and Channel 1 was a Halo monitor. I have never seen such an output from the GEM detector when exposed to beam. It seems we are unable to have the GEM detector in place when the pulsed 10 mA beam is tuning. I suspect this killed the detector on Aug 6.


Gas was flowing through both detectors today. In order to reduced the pick up noise, It was suggested to wrap detectors into the aluminum foil.

Tomorrow is a power shutdown in EEL, CEBAF and some other building. I will be unable to work there. I will get the scaler from counting room.


Below are the scope images of the noise before and after aluminum foil:

BeforeAlfoilnoise.pngAfterAlfoilnoise.pngAfterAlfoilnoise 1.png

Signals from the detector are following:

AfterAlfoilsignal.pngAfterAlfoilsignal 1.png



Turned Nauvoo on today. Foils were changed yesterday. When looking at TrigOut instead of seeing the positive pulse i am getting negative pulse, and no signal on strips. The last GEM foil acts like an anode(it collects the charge). I forgot to take the scope picture, but thats what i observed.


Changed the shorted GEM foil on Nauvoo, but still no positive signal on TrigOut. I saw negative signal.


Today worked on I2C. Gumstix, I2C board and power supply were installed in the NIM module. NIM module is in the NIM bin. The breakout box and two VFATs(64 and 112) are in the box under the NIM bin.

GumstixI2CNIMModule.jpgGumstixI2CNIMModule 1.jpg

Got Timing Filter Amplifier, couldnt find scaler. There was no use for integrator on Timing Filter Amplifier.

Nauvoo detector is open right now. I will apply voltage on GEM tomorrow and check the voltages again across the GEM foils.


Urim measurements

Got scaler and discriminator. Made measurements of GEM drift voltage vs rate. Used only cosmic rays.

The result is shown below:

GEMDRIFTHVvsRate 24-08-2010.jpg

GEMDRIFTHVvsRate 25-08-2010.jpg

The rate only doubled Dr. Forest. I did it for 3270 Volts.

Urim should be ready to install in Hall C after you try a source and wrap it in tin foil. Cut an opening in the tin foil for a window.

Fe-55 Source use

Iron-55 decays via electron capture to manganese-55 with a half-life of 2.737 years. 60% of the time an Auger electron is emitted. 8.2% of the time a 5.9 keV photon is emitted 2.9% of the time a 6.5 keV photon is emitted

A 126 keV photon comes off with a relative intensity of 1E-7.

Activity of Gamma, x-ray source. [math]300 \mu C \times \left ( 3.7 \times 10^{10} decays/sec \right ) = 1.1 \times 10^7 decays/sec = A_0[/math] as of 6/24/04.

Half life = 2.73 years

[math]A = A_o e^{-\lambda t} = 1.1 \times 10^{7} decays/sec e^{-6/2.73} = 1.2 \times 10^6 decays/sec[/math]

[math]E_{\gamma} = 126[/math] keV

TORI Data (1999) Gammas from 55Fe (2.73 y 3)

Eg (keV)    	Ig (%)    	Decay mode
125.95 1 	1.28E-7 2 	e 

X-rays from 55Fe (2.73 y 3)
E (keV)   	I (%)    	Assignment
0.556  	0.037 10  	Mn Ll
0.568  	0.025 6  	Mn Lh
0.637  	0.028 7  	Mn La2
0.637  	0.25 6  	Mn La1
0.640  	0.0022 6  	Mn Lb6
0.648  	0.19 5  	Mn Lb1
0.720  	0.011 3  	Mn Lb4
0.720  	0.017 5  	Mn Lb3
5.770  	6.9E-06 4  	Mn Ka3
5.888  	8.5 4  	Mn Ka2
5.899  	16.9 8  	Mn Ka1
6.490  	1.01 5  	Mn Kb3
6.490  	1.98 10  	Mn Kb1
6.536  	0.00089 5  	Mn Kb5
6.539  	8.5E-08 5  	Mn Kb4

NIST data tables says:

A .125 MeV photon has a Range in copper of = [math]3.2 \times 10^{-2} g/cm^2[/math]

Density Copper = [math]8.92 g/cm^3[/math]

Range = [math]3.2 \times 10^{-2} g/cm^2 / 8.92 g/cm^3 = 3.5 \times 10^{-3} cm = 1.4 \times 10^{-3} inches = 1.4[/math] mils

How thick is the GEM copper cathode?

Definition of Range:

Def of Range (R)
The distance traveled before all the particles energy is lost.
[math]R \equiv \int_0^T \frac{dE}{\frac{dE}{dx}}[/math]
= theoretical calculation of the path length traveled by a particle of incident energy [math]T[/math]
Note units: [math]\left [ R \right ] = \frac{g}{cm^2} ; \left [ \frac{dE}{dx} \right ] = \frac{MeV \cdot cm^2}{g}[/math]

At 0.126 MeV

[math]\frac{dE}{dx} = 2.387 MeV cm^2/g = 21.292 MeV/cm[/math]

If the copper is 5 microns thick then

[math]E_{loss} = 21292 keV/cm \times 5 \times 10^{-3} cm = 106 keV \Rightarrow [/math]photon energy would be about 20 keV when it sees drift region

What is Cathode thickness?

Is the Fe-55 source sealed or open. Sealed source would attenuate photons more.

The fraction of photons surviving a distance x is given by

[math]\frac{I}{I_0} = e^{-\mu x}[/math]


[math]\mu[/math] = total absorption coefficient = 1/(mean free path) = [math]\frac{N \rho}{A} \sigma[/math]

N = Avagadros number [math]\rho[/math] = density of copper A = molar weight [math]\sigma[/math] = cross-section per atom

A 6 keV photon has [math]\mu/\rho = 115.2 cm^2/g \Rightarrow \mu[/math] = 1027.6 /cm

A 126 keV photon has[math] \mu/\rho=~0.3 cm^2/g \Rightarrow\mu [/math] ~ 3 /cm

[math]\left . \frac{I}{I_o}\right |_{6 keV} = e^{-1027.6/cm \times 50 \times 10^{-3} cm} = 4 \times 10^{-23}[/math]

[math]\left . \frac{I}{I_o} \right |_{126 keV} = e^{-3/cm \times 50 \times 10^{-3} cm} = 0.86[/math]

If the copper cathode is 5 microns and not 50

[math]\left . \frac{I}{I_o}\right |_{6 keV} = 6 \times 10^{-3}[/math]

[math]\left . \frac{I}{I_o} \right |_{126 keV} = 0.98[/math]

the link below takes you to the mass attenuation coefficients for copper



The 2nd column is the mass attenuation coefficient [math]\mu/\rho[/math] and the third column is the energy absorption coefficient [math]\mu_{en}/\rho[/math]

Copper Z = 29


      (MeV)      (cm2/g)     (cm2/g)

   1.00000E-03  1.057E+04  1.049E+04 
   1.04695E-03  9.307E+03  9.241E+03 
   1.09610E-03  8.242E+03  8.186E+03 
L1 1.09610E-03  9.347E+03  9.282E+03 
   1.50000E-03  4.418E+03  4.393E+03 
   2.00000E-03  2.154E+03  2.142E+03 
   3.00000E-03  7.488E+02  7.430E+02 
   4.00000E-03  3.473E+02  3.432E+02 
   5.00000E-03  1.899E+02  1.866E+02 
   6.00000E-03  1.156E+02  1.128E+02 
   8.00000E-03  5.255E+01  5.054E+01 
   8.97890E-03  3.829E+01  3.652E+01 
K  8.97890E-03  2.784E+02  1.824E+02 
   1.00000E-02  2.159E+02  1.484E+02 
   1.50000E-02  7.405E+01  5.788E+01 
   2.00000E-02  3.379E+01  2.788E+01 
   3.00000E-02  1.092E+01  9.349E+00 
   4.00000E-02  4.862E+00  4.163E+00 
   5.00000E-02  2.613E+00  2.192E+00 
   6.00000E-02  1.593E+00  1.290E+00 
   8.00000E-02  7.630E-01  5.581E-01 
   1.00000E-01  4.584E-01  2.949E-01 
   1.50000E-01  2.217E-01  1.027E-01 
   2.00000E-01  1.559E-01  5.781E-02 
   3.00000E-01  1.119E-01  3.617E-02 
   4.00000E-01  9.413E-02  3.121E-02 
   5.00000E-01  8.362E-02  2.933E-02 
   6.00000E-01  7.625E-02  2.826E-02 
   8.00000E-01  6.605E-02  2.681E-02 
   1.00000E+00  5.901E-02  2.562E-02 
   1.25000E+00  5.261E-02  2.428E-02 
   1.50000E+00  4.803E-02  2.316E-02 
   2.00000E+00  4.205E-02  2.160E-02 
   3.00000E+00  3.599E-02  2.023E-02 
   4.00000E+00  3.318E-02  1.989E-02 
   5.00000E+00  3.177E-02  1.998E-02 
   6.00000E+00  3.108E-02  2.027E-02 
   8.00000E+00  3.074E-02  2.100E-02 
   1.00000E+01  3.103E-02  2.174E-02 
   1.50000E+01  3.247E-02  2.309E-02 
   2.00000E+01  3.408E-02  2.387E-02 

Setting on Amplifier and discriminator:

Amplification is X20 and 10 on a nub. Integration=20ns and diff=out. Pulse divided, one and goes to discriminator and the other one into the scope. The discriminator threshold is set to 45 mV.


High Voltage distribution for GEM.

GEM HV Dist Net.jpg

Applied 500 Volts on GEM.

The measured voltage on each side of the each GEM foil is presented in a table.

GEM Foil Measured Voltage(Volts) Nauvoo Measured 10 x 10 cm Board Voltage
VGem in 500 500
G1T 256 248
G1B 422 473
G2T 148 232
G2B 237 415
G3T 78 217
G3B 104 371

I was expecting the voltage to decrease with respect to ground as you go down the voltage divider.

It is decreasing. By G3 i mean the last GEM foil.


Got CAT5 cable for I2C. Need connectors.

Changed resistors on HV board of Nauvoo, still no luck. Had to take open Urim, to check the voltage distribution, it is the same as on Nauvoo.

Dont know what is the reason, the foils are new.

Instead of positive pulse getting negative pulse on trigout again.



Works since yesterday. Changed foils.

Nauvoo 30-08-2010.jpgNauvoo 30-08-2010 1.jpg

Voltage = 3475/3200 Volts

Amplification= X20, 12.5 on a nub.



Discriminator threshold = 80 mV

Time (mints) # Counts Rate (Number of Events/sec)
13 1002 1.28
16 1233 1.28
14 914 1.1

[math]Rate = 1.22 \pm 0.07 [/math](Numberof#/sec)


UrimVerticalPosition 30-08-2010.jpg

Voltage setting on Urim = 3245/2945 Volts

Time (mints) # Counts Rate (Number of Events/sec)
11 1357 2.056
7 859 2.045
7 862 2.052

Vertical vs Horizontal

Position Rate (Number of Counts/sec)
Vertical [math]Rate = 2.05 \pm 0.004[/math]
Horizontal [math]Rate = 2.15 \pm 0.07[/math]

The bracket is attached to Urim.

UrimBracket 30-08-2010.jpg

Remaining tasks

bubbler holder , need 2 more shielded ribbon cable, new aluminum foil for detector in order to shield it.

High Voltage Supply: The channel number 2 on hv supply doesnt go above 3000Volts. Suggest, to use 0 and 1 channels for Nauvoo and 3&&2 for Urim.

There is only one new breakout box in Hall, need to bring second one.

1.)check cosmic rate on both detectors and measure noise ( max 10 mV peak to peak)

Detector Drift HV GEM HV
Urim -3245 -2945
Nauvoo -3450 -3150

2.) Attach adapter boards

3.)I2C checkout

4.) Look into Al shielding

5.) install shielded ribbon cables, work on readout

6.) install bubbler if still not done.

Co-60 source

A Co-60 source was placed on top of the GEM detector kapton foil window. The button source activity was 0.6 microCurie in 2004. The source generated a rate of 70 Hz.

Activity of Gamma source. [math]6 \times 10^{-7} C \times \left ( 3.7 \times 10^{10} decays/sec \right ) = 2.2 \times 10^4 decays/sec = A_0[/math] as of 6/24/04.

Half life = 5 years

[math]A = A_o e^{-\lambda t} = 2.2 \times 10^{4} decays/sec \times e^{-6/5} =6686 Hz [/math]

According to http://ie.lbl.gov/toi/nuclide.asp?iZA=270060

Co-60 activity is from mainly 2 photons 1173.237 keV and 1332.501 keV.

A 1.2 MeV photon has[math] \mu/\rho=0.0526 cm^2/g \Rightarrow\mu =[/math]0.465 /cm

[math]\left . \frac{I}{I_o}\right |_{1.2 MeV} = e^{-0.465/cm \times 50 \times 10^{-3} cm} = 0.977[/math]

If the above is correct , the Co-60 source is emitting 1.2 MeV photons at a rate of 6.5 kHz.


Use cdaq@cdaql6 to readout V1495.

terminal server port

To get to qwvme11

telnet hctsv7 2006

To go to Gumstix

telnet hctsv11 2005

Checking I2C controls

ssh root@qwgemgumstix

cd bin

ports 112 and 64 have VFAT cards on them

flipping sleep block for VFAT at I2C address 64

 echo "p 64 0 0 flip" | ./flipbit.arm
 echo "p 112 0 0 flip" | ./flipbit.arm

The 2 VFAT cards are responding.

My SCSI doesn't seem to work anymore with my powerbook. Try to debug tonight.

I got the DAQ running on cdaql6.

I am sending a trigger down to the V1495 which triggers the VFAT cards.

I got the error message on the ROC

interrupt: v1495ReadEvent: Error: header for word 3 from data packet != 0xE

EB1 crashed. I am triggering at about 200 Hz.

Wrote data file

Paul King paid me a visit and corrected my CODA choices so I could write a file. Apparently I had chosen Session and Run configuration wrong

Proper CODA settings for standalone V1495 runnging

Session = cdaq COOL configureation = V1495_l6

To start DAQ

1.) run codamaster

2.)choose v1495_l6 from the EXPID menu presented by coda master

3.) launch all the components

4.) choose "V1495_l6" from the session menu in runcontorl

5.) select the "cool" menu from the "Configuration" menu.

then select "V1495_l6" from the popup menu

6.) follow the usual download, prestart , and run

wrote the data file

[cdaq@cdaql6 ~]$ ls -lh /local/data1/v1495_l6_5424.dat.0 -rw-r--r-- 1 cdaq c-cdaq 64K Sep 18 19:50 /local/data1/v1495_l6_5424.dat.0

All is not perfect. I get the error message

interrupt: v1495ReadEvent: dataFIFO is empty

It looks like the VFAT is missing some of the triggers I send it when I look on the scope.

Try to debug tomorrow by doing single triggers and use the functions


the above function should return the number of events waiting to be read out. So hit the trigger button and make sure the above function returns the value of "1"

Then use the command

-> v1495StatusPrint

0x1b090b0 (tShell): V1495[0]: #B[24] #F[1/131] B/s[24] F/s[1]
0x1b090b0 (tShell):   LastCap[12]: 0x1b090b0 (tShell): A2AC 0x1b090b0 (tShell): C720 0x1b090b0 (tShell): 0A71 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 907D 0x1b090b0 (tShell): 
0x1b090b0 (tShell): Event Count: 114 ; Chip ID : 0xA71
0x1b090b0 (tShell): value = 32 = 0x20 = ' '
-> V1495[1]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b090b0 (tShell):   LastCap[0]: 0x1b090b0 (tShell): 
0x1b090b0 (tShell): V1495[2]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b090b0 (tShell):   LastCap[0]: 0x1b090b0 (tShell): 
0x1b090b0 (tShell): V1495[3]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b090b0 (tShell):   LastCap[0]: 0x1b090b0 (tShell): 
0x1b090b0 (tShell): V1495[4]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b090b0 (tShell):   LastCap[0]: 0x1b090b0 (tShell): 
0x1b090b0 (tShell): V1495[5]: #B[24] #F[1/131] B/s[24] F/s[1]
0x1b090b0 (tShell):   LastCap[12]: 0x1b090b0 (tShell): A2AC 0x1b090b0 (tShell): C720 0x1b090b0 (tShell): 5CEA 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 0000 0x1b090b0 (tShell): 74A8 0x1b090b0 (tShell): 
0x1b090b0 (tShell): Event Count: 114 ; Chip ID : 0xCEA

You should see chip IDs like above.


Missing triggers

I noticed yesterday that some triggers did not return data packets. Let's try to debug this.

I have 2 VFAT cards in port 64 and 112. As seen from yesterday using the v1495 library function v1495StatusPrint() on the ROC The CHIP ID's are 0xCEA and 0xA71. This agrees with what I2C is telling me.

I will now give the Readout one trigger at a time and check if the V1495 has any data on it using the



First run the script VFAT.setup from the qwgemgumstix. The script is in the subdirectory /home/root/bin


Now I will work from the ROC.

First Initialize the V1495

 -> v1495Init(0x09330000)
0x1b08930 (tShell): v1495Init: v1495 Module has been successfully initialized.

0x1b08930 (tShell): v1495 module has been reset: 

value = 0 = 0x0

Now I reset the v1495 module to clear all its buffers

-> v1495Reset()
0x1b08930 (tShell): v1495 module has been reset: 

value = 0 = 0x0

Now Check to see if there is any data before I push the single trigger button on the gate generator.

-> v1495DataReady()
value = 0 = 0x0

Now push the trigger button once

-> v1495DataReady() value = 1 = 0x1

Now I check what is in the buffer using

-> v1495StatusPrint()
0x1b08930 (tShell): V1495[0]: #B[24] #F[1/2] B/s[24] F/s[1]
0x1b08930 (tShell):   LastCap[12]: 0x1b08930 (tShell): AE46 0x1b08930 (tShell): C010 0x1b08930 (tShell): 0A71 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 1C38 0x1b08930 (tShell): 
0x1b08930 (tShell): Event Count: 1 ; Chip ID : 0xA71
0x1b08930 (tShell): V1495[1]: #B[0] #F[0/0] B/s[value = 0] F/s[032]
0x1b08930 (tShell = 0x):   LastCap[020]: 0x1b08930 (tShell = '): 
0x1b08930 ( tShell): V1495[2]: #B['0] #F[0/0] B/s[
0] F/s[0]
0x1b08930->  (tShell):   LastCap[0]: 0x1b08930 (tShell): 
0x1b08930 (tShell): V1495[3]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b08930 (tShell):   LastCap[0]: 0x1b08930 (tShell): 
0x1b08930 (tShell): V1495[4]: #B[0] #F[0/0] B/s[0] F/s[0]
0x1b08930 (tShell):   LastCap[0]: 0x1b08930 (tShell): 
0x1b08930 (tShell): V1495[5]: #B[24] #F[1/2] B/s[24] F/s[1]
0x1b08930 (tShell):   LastCap[12]: 0x1b08930 (tShell): AE46 0x1b08930 (tShell): C010 0x1b08930 (tShell): 5CEA 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): 0000 0x1b08930 (tShell): F8ED 0x1b08930 (tShell): 
0x1b08930 (tShell): Event Count: 1 ; Chip ID : 0xCEA

I see the CHIP ID's which I saw when using the I2C interface.

Data is still wiating to be readout, doing the above function did not alter the V1495 buffers

-> v1495DataReady() value = 1 = 0x1

To move the data out of the v1495 buffers you can do a ReadEvent

-> v1495DataReady()  
value = 1 = 0x1
-> v1495ReadEvent()  
value = 84 = 0x54 = 'T'
-> v1495DataReady()  
value = 0 = 0x0
-> v1495ReadEvent()  
0x1b08930 (tShell): v1495ReadEvent: dataFIFO is empty
value = 0 = 0x0

I sent trigger to the v1495 and monitored the scope output.

Whe I started I observed that about 30% of the triggers were missed as seen on the scope.

Changing the shielded cable to an unshielded seemed to drop that to 10%. Perhaps the missed triggers are cable related.

I think I will put connectors onto the new shielded ribbon cable and see if things improve.

Rad damage to VFAT chip?

I took out the two working VFATs and inserted a VFAT card which was in the R1 hut during the summer commissioning run.

I2C was still working, I could set registers, but I did not observe any LVDS output (I believe it was not working before though).

Test 2nd breakout box

Tamuna's NIM Module only has 1 power output. Should we tee it off to supply 2 breakout boxes, I am not sure if it can supply the current. May need to test

I think you cant tee it.

It depends on how much current the power supply is rated for. I think we need at least 1.2 mA per breakout board. So if the power supply delivers 3 mA and maintains 2.5 volts we would be able to tee it.

I wonder if Warren put in the voltage protection diodes in the latest version of the breakout board?

I think I also need to work on the I2C control of 2 boards with one gumstix or I could ask Tamuna to build another NIM module.

Test 2nd breakout box in R1 Hut

It seems there is a lot of pickup on the flat ribbon cable (peak-peak noise of about 400 mv with and RMS of 40 mv).

R1Hut LVDS FlatRibbonCableNoise 9-19-2010.png

Now hook a ground wire between the scope and a Ground pole in Hall C.

BNC trig out cable is on Channel 1, not hooked to anything. Grounding the scope reuces the noise to 60 mV peak-peak.

The unshielded ribbon cable is hooked to Channel 2

GoundScope2HallC BNCCH1 FlatRibbonCableCH2Noise 9-19-2010.png

BNC trig out cable is on Channel 1, not hooked to anything

The unshielded ribbon cable is hooked to Channel 2

The shield from a shielded ribbon cable is attached to Scope.

GoundScope2CableShield BNCCH1 FlatRibbonCableCH2Noise 9-19-2010.png

Shielded cable ungrounded

9-19-2010 856.png

Shielded cable grounded

9-19-2010 857.png

16 MHz LVDS clock on either shielded flat fibbon cable or unshielded with shielded ribbon cable grounded to scope

9-19-2010 904.png

16 MHz LVDS clock straight out of V1495

9-19-2010 939.png

The clock pulse is being attenuated by a factor of 3. You need 200 mV differentials to drive LVDS and both cables attenuate the pulse to below 130 mV.
The grounding the ribbon cable shield to the scope drops the noise from 400 to at least 30 mV. Similar noise reduction was observed if you only use shielded cable in the R1 hut area.


Made new shieled ribbon cables to take signals from breakout board to VFAT cards

started taking a run with VTAS plugged into 16 and 112


I think the FIFO empty messages started killed the DAQ after about 200 events.

The above missing triggers is because the trigger pulse needs to have a width that is at least 1.5 MCLK cycles

maybe its because the trigger pulse was not 1.4 clock pulses wide.

Make HClog entry for Paul King


Cat 6 -vs- ribbon cable attenuation

The 28 guage ribbon cable wire attenuates a 20 MHz signal 4.8 dB/100 ft.


The scope observations from 9/19/10 suggest that

dB = 20 log(400 mV/120 mV) = 10.45 dB/100 ft > 4.8 dB/100 ft?

Cat 6 attenuates 20 MHz signal 2.2 dB/100 ft (careful units are in meters in document below)

File:Cat6Attenuation 060-490GY.pdf

V1495 connector pin assignment



A MCLK of 6.3 MHz or less will drive the one VFAT card on the breakout box. The scope picture below shows the output at the break out box from a VFAT card installed at address 112.

20100927 1019.png

Zooming in to the MCKL pulse and comparing what comes out of the V1495 (MCLKin) and out of the 100 FT JLab shielded, round ribbon cable (MCLKout)

20100927 1033.png

I notice the V1495 output at JLab has a peak-peak value of 420 mV. Perhaps we can run at a higher frequency using the V1495 at JLab.

Now lets try installing 6 VFAT card to check that the V1495 output is not pulled down using the extra cards. I believe the V1495 delivers a separate MCLK pulse to each VFAT card. So this is a test of the V1495's drivers for each I/O channel.

The VFAT output on the breakout board still worked with all 6 VFATs being driven by the V1495.

Now lets attach the long cable to the digital output from the Breakout box and measure its attenuation

Below is a measurement off the breakout box

20100927 1044.png

Below is a measurement out of the shielded round ribbon cables from JLab.

20100927 1050.png

There is less attenuation but the capacitance is clearly rounded the logic pulse. Is this too much to prevent flipping a V1495 input? Probably not if this worked before.


Checking out detectors at JLab.

Simone tells me they put HV on both Detectors last Friday and Nauvoo appeared to spark.

Today I see Nauvoo sparking at 2600 Volts on GEM.

Urim appears to be working well still.

Urim is attached to the Hall C rotator on SLider A and the trigout signal is being sent directly to the upstairs DAQ shed.

To see a ~1Hz rate I have set the HV to

Detector Drift HV GEM HV
Urim (GEM A) -3400 -3100

Urim HallC 20100929 1227.png

After Lunch I will put Urims trig out signal into the timing AMplifier Tamuna set up and look for signals. For now I lower the voltage to 3250:2950.

I am leaving Nauvoo at 2800:2500.

I connected up amplifer and set discriminator to 60.0 mV and saw a 2 Hz rate when using HV = 3400:3100.

The signal out of the amplifier looks like

AmpOut20100929 1524.png


Now I work on readout.

I set Agilent to 6 MHz and download new firmware to qwvme11.

Pulled the round, shielded , ribbon cables to R1 and installed 6 VFAT cards on Urim.

LVDS data out pulse seen on V1495 copy using rounded ribbon cables.

VFATdataOut 20100929 1525.png


Working on setting discriminator levels on the VFAT.

Spent a lot of time looking at signals.

Took scope picture of noise from the sliders. Channel 3 is connected directly to a breakout board mounted to the GEM detector but not plugged into LVDS signals. THe power is connected to the breakout board and thus a ground through the doghouse racks.

With the sliders off I see the following. The red trace is a FFT of channel 3.

20100930 1625.png

Turn on the sliders using the computer (this puts voltage on them) and the signal gets worse

20100930 1628.png

The frequency of the beats seems to be about 24kHz

The above noise prevented me from seeing the digital output of the VFATs when measured at the breakout box. They were there but the 200 mV signals were hard to see with the 128 mV 240 kHz noise signal.

I decided to look at the copies of the VFAT data out signals which come out on the inner cable in the V1495's port C. I could clearly turn VFAT cards off individually and set the threshold by hand. I set 4 out of the 6 VFAT cards to a noise level. For some reason there wasn't a digital out from the V1495 for chips at I2C addresses 80 nor 96.

Tomorrow try to check the 2 remaining VFATs. May need to swap cards or breakout boards.

The I2C communication appears to fails sometimes. The VFATs are still running suggesting that the problem is at the gumstix level. Perhaps the terminal server connection was not responsible for the failure yesterday.


The above I2C problem appears to be due to an undervoltage to the Breakout box. I turned up the voltage to 3.1 Volts instead of 2.5. The LED is still not on but the I2C to the VFAT is more stable.

R1 gas consumption

I observed that the R1 gas bottle gauge changed by 50 Psig over the last 24 hour period.

Self trigger timing

Let's play with the latency of the chip to see if we have cosmic hits.

We turned Urim up to 3400:3100, saw signals at about 1 Hz, sent the trigger downstairs.

Simon's previous cable length measurement says it is 505 ns for a signal to travel from Urim to upstairs.

So we should set the latency to be 1010 ns since we are sending the the trigger signal back down to the V1495.

The latency setting tells the VFAT how many clock cycles to go back in time to look for data in the SRAM. So it depends on MCLK

MCLK is currently set to 4.13 MHz = 242 ns => latency = 5.

How long does is take for the V1495 to convert the trigger input on G1 to an output pulse on Port A?

V1495 Internal delay

The scope picture below indicates that when using MCLK = 4.13 MHz the trigger out of the V1495 is about 900 ns after it recieves the G1 input TTL pulse.

2010100110 0342.png

Run 5551

Starting a run using Hall C's CODA on cdaql6.

wrote data to


The rate was about 2.5 Hz according to the CODA GUI

There are still triggers getting dropped by the V1495.

Run 5552

Starting a run using Hall C's CODA on cdaql6.

wrote data to


The rate was about 2.5 Hz according to the CODA GUI

There are still triggers getting dropped by the V1495.

3495 events

Run 5553

Set latency to 0x0a

Starting a run using Hall C's CODA on cdaql6.

wrote data to


data rate has increased, noise in the Hall?

Event Builder crashed.

752 events

Run 5554

Set latency to 0x0a

Data rate is 2-3 Hz

Starting a run using Hall C's CODA on cdaql6.

wrote data to


There was about a 0.5 Hz or less trigger rate with the detector off.
Need to raise discriminator level on Urim's trigout it was set to about 60 mVs.


Tamuna arrived on last week and used the GEM foils from Nauvoo to get Urim working again.

SHe noticed that the HV ramp was set to 10 V/sec. It is possible that the previous users did not ramp up a 2 V/sec when it was needed. I will change the ramp default to 2 V/sec to avoid users from having this problem again. We suspect that the users ramped the voltage too quickly and caused discharges.

Below is a new picture of Urim signal at [math]HV_{Drift}[/math] = -3350 and [math]V_{GEM}[/math] = -3050.

Urim Signal 11-21-2010.png

To see the above signal at the above high voltage you need to cover the detector with a Faraday cage (Al foil around detector) an apply a 20 MHz high pass filter.


R1 Detector install

Entered hall to identify test stand location for GEM detector Urim.

We will use the cable tray rack behind the HKS to mount the GEM. There is a patch panel nearby and we have moved a bottle of Ar/CO2 gas to that location.

I sent the GEM trigout pulse over to the doghouse using cable 408 (GEMB, #196) and into the timing amplifier. The timing amplifier output was left coming up to the cage on cable 409 (GEMAtrig). This going into a discriminator which goes to a scaler in the counting house.

The HV cables have been plugged into 27d or 26d port 0 and 2. I need to double check this.

I plugged the "GEM" HV into port 0 and the "Drift" into port 2.

We need to insert the timing amplifier from the doghouse.

So send Urim's trigout pulse to the doghouse using the cable patched into port 407 (GEMA trig). In the doghouse take GEMA trig cable and send it to the timing amplifier input. The timing amplifier output then goes to the GEMB trigout cable which is sent to port 408 at the patch panel.

Installed 2 VFAT cards

I installed 2 VFAT cards on a breakout box in the doghouse at address VFAT16 and VFAT112.

I had to lower the DC voltage sourced by the VFAT power supply from 3.1 to 2.56 V.

I plugged the LVDS cables into the V1495 but I didn't check if there were signals there. I do see that the copies are still being sent up to the 2nd floor counting house cage.

Beam tests at patch panel

Urim was mounted just below the cable tray near the patch panel.

1.) 5 nA as measured by the FC

Discr=17.5 mV, HV=-3325,3025, time=22:34 start, stop 22:55, 15202 counts => 12.1 Hz another run time = 22:57 start, 23:14 top, counts 12858=>12.6 Hz beam off: 1930/180=10.7 Hz

2.) 19.5 nA

Run # 7470, In Qweak ntuples they take beam on and beam off data in the same data file. The beam on data is marked suing the ntuple variable scandata1=1, the beam off data are labeled with the variable scandata1=2. All the data have a label "clean data" to indicate

Discr=17.5 mV, HV=-3325,3025, time = 300 sec Counts = 6240 = 20.8 Hz

second attempt: 140 sec , 2891 counts => 20.7 Hz

package 2= trigger scintilator= 50 kHz

beam off: 4:17:59 = 258 second, counts = 2662 => 10 .3 Hz package2 = 500 Hz

3.) 41.2 nA

run #7471

Discr=17.5 mV, HV=-3325,3025, time = 300 sec, counts=9046 => 30 Hz

time 4:35=275 second, counts= 10710, => 39 Hz

packag2= 140 kHz

package2= 216 KHz

The package 2 and GEM saw the count rate increase with over the run period

Beam off:

180 seconds, 1722 counts => 9.6 Hz

package2 = 650 Hz

4.) 80 nA

63 Hz, 65 Hz

katherine does discriminator threshold change on her trigger scintillator (package 2) which will impact her rates. She raised the threshold.

Package_2 Hz GEM TrigOut (Hz) Run Number Beam Current(nA) Beam ON/OFF
730 1794/180=10 7472 0 OFF
410.510 18179/200=91 7473 80 ON
353.060 6884/180=38 7473 80 ON
376.871 6528/180=36.3 7473 80 ON
455451 3370/40=84 7473 80 ON
442204 8250/105=79 7473 80 ON
446463 13132/175=75 7473 80 ON
81.045 6464/180=36 7475 60 ON
65.000 5707/180=32 7475 60 ON (FSD Trip)
35.243 2962/181=16 7476 5 ON
26.154 2726/180=15 7476 5 ON
24.320 2613/180=14.5 7476 5 ON

Due to FSD trip wasn't able to count events for 60 nA beam current setting.

The rest of the night beam current should be 5 nA.

Results of beam current change in Hall C

UrimOutputInCage 11-22-2010.png

as reference in the HClog entry:


UrimCountRate-vs-BeamCurrent 11-22-2010.png

File:XmgraceUrimCountRate-vs-BeamCurrent 11-22-2010.txt


During down time I turned on the detector to see a cosmic rate.

The noise level increased from about 20 mV peak-peak with 3 mV RMS to about 30 mV peak-peak with about 3 mV RMS.

I increased the descriminator threshold from 17.5 mV to 27.5 mV.

I ramped up at 2V/s to 2kV, waited 50 minutes and ramped up to Drift/GEM = -3325/-3025 V.

The cosmic rate was low at 0.8 Hz.

Ill try lowering the descriminator first.

i lowered the discriminator to 27 mV and didn't like the signals. The greater than 100 ns ones were not convincing ionization events, they did go away though when the detector was turned off (curious).

I increased Urim's HV to -3350/-3050 and set the discriminator back to 27.5 mV.

Rate = 885/360 = 2.5 Hz

Rate = 865/360 = 2.4 Hz

Rate = 1798/736 = 2.4 Hz

I now turn the Drift voltage to equal the GEM voltage and cound

Rate(bckgrd) = 30/521 = 0.06 Hz

Rate(bckgrd) = 41/735 = 0.06 Hz

Rate(bckgrd) = 30/340 = 0.09 Hz

Rate(bckgrd) = 52/513 = 0.1 Hz

Rate(bckgrd) = 37/367 = 0.1 Hz


Gas was not flowing into Urim over the weekend. Arshak said he saw the bottle turned off but didn't start the gas flowing because he thought I turned it off. I turned the gas on at 9 am Monday and set a high flow rate.

I installed the new Gumstix computer into the doghouse. The network cable inside the NIM box had worked its way out of the connector enough to prevent the network from coming up. After some debugging I discovered this. You need both a green light and a flashing yellow light in order to know that it is plugged in. I only saw the green light and was fooled into thinking it had a good connection.

Arshak pulled cable over to R3. I didn't see an RJ45 cable for I2C though. The stand is in the hall and is configured to use the mounting fork. Nuts for mounting the breakout board and adapter plate were not found, I had Tamuna send FedEx some from ISU.

The detector was placed on top of a table near the patch panel. Gas was flowing when I left the hall at 5pm.


V1495 DAQ on cdaqL6

1.) Restart qwvme11

on cdaql6 run "firefox qwpowerstrip3" and tell port 8 to power cycle.

"telnet hctsv11 2006" didn't work so I did

"telnet qwvme11" and I saw that the ROC had booted.

2.) codamaster

started codamaster and selected "v1495_l6"

I then started up all the usual processes.

For session I selected "cdaq"

Then under the "cool" menu I selected "v_1495_l6"

I then did "download" and "prestart"

3.) run 8212

I had a 2 Hz trigger and wrote the file


The data file had the event but there was no data in the V1495. The VFATs were turned off.

Let's turn them on.

login to qwgemgumstix

cd bin


Only 2 cards are in at address 16 and 112.

4.) run 8213

I now see an event in the data file which has 2 VFAT cards and a bunch of zeros.


""BUT" there were some empty events in the V1495.

Last time this was due to a timing issue.

I looked at the data file and saw a good first event with the right VFAT chip IDs.

But the next event did not have the VFAT card in address 16.

5.) I restarted CODA and chose the seeion "qweak_cdaql6"

THings worked just as well

interrupt: v1495ReadEvent: dataFIFO is empty

The above problem happens when the timing is off.

If I remember right the trigger width needs to be at least a clock cycle and 1/2 in order to be seen.

PMT paddles

Brad Sawatzky loaned 2 scintillator paddles to the effort

Paddles are labeled PMT01 and PMT03. The paddles are 5" wide x 13" long x 1 cm thick

I saw cosmic pulses on PMT03 at -1250 and PMT01 at -1300 Volts, respectively.


Installed bubbler so shift checklists can monitor the gas flow.

Installed HV and trigout channels. HV0 = GEM, HV03 = Drift. So higher channel number gets higher voltage.

I was unable to drive the LVDS signals from the doghouse to R3. Even at the lower frequencies, the signals were intermitant. I will try to look more into this on Thursday and Friday. First get 2 VFAT cards working in the doghouse just to be sure the system is still working. Then try it ove by R3.

Noise reduction

A ground cable attached from the HV bulkhead connector to the Faraday cage reduced the noise from a peak-to-peak of 210 mV to about 68 mV. The unshielded LVDS cables would increase this to 100 mV.

Noise 12152010 GEMTrigOut.png


Turning on Urim

Turned Urim up to 2kV at 9:11 am today. Some 100 mV level (post amplifier) pulses were observed happening once a minute or so but I think this was not related to the GEM detector but just picked up off the ground.


The noise on the Post amplified Trigout pulse was 40 mV peak to peak as seen down in the doghouse. If the MCLK frequency went to 8 MHz then the peak-peak noise went to 60 mV. It went back down to 40 mV at 40 MHz.

The noise observed on the amplified GEM trigout pulse upstairs in the counting house cage. The Amplifier is set to x20 and a 5o ns integration time constant. The peak-to-peak noise is at least 30 mV with an RMS of 12 mV. So set the disciminator to at least (16 + 12 ~ 30 mV).

Noise 12162010 GEMTriout AtCage.png

With the HV off and the discriminator set to 30 mV I saw a rate of at most 0.02 Hz. This rate went to 0.5 Hz at a threshold of 25 mV and 10 kHz at 20 mV.

Signal 12162010 3100-3400.png

Threshold setting -vs- HV

Urim HV 25 mV Thrsh 30 mV thresh 35 mV 40 mV 45 mV
3100:-3400 1 Hz 0.85 Hz 0.36 Hz 0.22 Hz
3125:3425 3.7 Hz 1.9 Hz 1.4 Hz 0.7 Hz


I observe the data patters which are copied to port C. I can see the data packets go away when I turn off the VFAT cards except for the one at 112. I see back-to-back data pulses on the V1495 monitor which was suppose to be from 112. It does not go away when I turn off the VFAT card.

The shielded cable seems to kill the signals when attached to the LVDS input to the Breakout board. This means the MCK/trigger pulses are not driving the VFAT cards.

The data packets go away when MCLK is below 2 MHz.


R1 Hut irradiated VFATs

11:54 Removed VFAT cards SN#0071 and SN#0073 from the R1 hut today. An activity of 0.5 mrad was observed from them and 0.8 mr from the G10 used to mount them. The beam had been off for at least 24 hours. Both cards responded to I2C reqests and returned their Chip IDs.

Changed VFAT power supply DC from 2.65 to 2.51 Volts

I was turning VFAT cards on and off when I lost I2C contact with all the cards. I had been turning them on and off several times and they were powered on all night.

Is it possible that the power supply is not reacting fast enough to the current drops? Check the effect of fast load changes on the power supply.

V1495 Error Message

-> v1495ReadEvent()
0x1ad8900 (tShell): v1495ReadEvent: Error: header for word 3 from data packet != 0xE

Changing the trigger gate width to be bigger than 1 clock cycle (but less than 3) seems to have made the problem go away.

VFAT data packet double pulsing

It looks like the VFAT at address 112 is sending double packets.

The second VFAT packet gets added to the end of the first read.

Data files

With the VFAT cards installed on the detector I attempted to readout the cards. The detector was at 2kV.

Run 8321

Turned off all VFATs

EMPTY data file stored at /local/data1/v1495_l6_8321.dat.0

Run 8322

turned on VFAT at addess 16 with chip ID 0x6a 0x98

stored at /local/data1/v1495_l6_8322.dat.0

Run8322 20101217.png

Run 8323

Turned VFAT at address 16 off and turned VFAT at address 80 on Chip ID :0xea, 0xdc

EMPTY stored at /local/data1/v1495_l6_8323.dat.0

Run 8324

Turned VFAT at address 16 off and turned VFAT at address 80 off VFAT at address 96 on Chip ID :0x71, 0xaa

EMPTY stored at /local/data1/v1495_l6_8324.dat.0

Event Builder: EB43 crashed

Run 8325

Turned VFAT at address 16 off and turned VFAT at address 80 off VFAT at address 96 on Chip ID :0x71, 0xaa

EMPTY stored at /local/data1/v1495_l6_8325.dat.0

interrupt: v1495ReadEvent: Error: header for word 3 from data packet != 0xE

Event Builder: EB43 crashed again

Run 8326

Turned VFAT at address 16 off and turned VFAT at address 80 off VFAT at address 96 off VFAT at 112 is turned on Chip ID :0x71, 0xe0

stored at /local/data1/v1495_l6_8326.dat.0

Run8326 20101217.png

Run 8327

Turned VFAT at address 16 off and turned VFAT at address 80 off VFAT at address 96 off VFAT at 112 is turned off, VFAT at 64 Chip ID :0xf1, 0xc0

EMPTY stored at /local/data1/v1495_l6_8327.dat.0

Urim Plateau

I turned Urim on again to measure the cosmic rate as a function of discriminator threshold.

Threshold setting -vs- HV

Urim HV 25 mV Thrsh 30 mV thresh 35 mV 40 mV
3100:-3400 3.8 [math]\pm[/math] 0.2 -.66 [math]\pm[/math] 0.07 0.33 [math]\pm[/math] 0.03 0.19 [math]\pm[/math] 0.02
3125:3425 1.6 [math]\pm[/math] 0.2 0.88 [math]\pm[/math] 0.03 0.52 [math]\pm[/math] 0.01
3150:3450 2.6 [math]\pm[/math] 0.2 1.8 [math]\pm[/math] 0.08 1.4 [math]\pm[/math] 0.1 1 [math]\pm[/math] 0.1

Urim Rate-vs-Disc 20101217.png

GEM Scintillators

Installed 2 scintillators with SHV and BNC

The GEM HV power supply channels HV0 and HV1 go to Scint2 and Scint3 respectively. Scint 3 is the downstream scintillator

GEM efficiency measurements on 1/2010



Efficiency of detectors PMTCoincidenceRate 23-01-2010.jpgEfficiency of GEM to respect of DC Rate 23-01-2010.jpg

Run plan for next time with beam

Pre-beam prep

  1. configure cables to prevent snags during slider motion
  2. set discriminator threshold with cosmics and sliders off
  3. measure time difference between a cosmic in R2 and in R1 (compare the pulse from the GEm trigout to the FOR from a R2 chamber)
  4. turn off urim and see if there are any triggers from discriminated trigout
  5. set discriminator so there are no triggers when the detector is off.
  6. turn detector on to produce cosmic triggers and do a latency scan while looking at digital out pulses on GEM B trigout cable.

Beam on

  1. leave detector off and out of position until R2 is turned on
  2. Check discriminator level with sliders off (should only be a 2 Hz cosmic rate)
  3. compare rates with R2,change HV +/- 50 Volts , and measure rates as a function of beam current, 0-100pA steps of 20 pA? see table below
  4. Measure time difference between R2 FOR and Urim Trigout pulse (take scope pictures and if possible TDC measurement)
  5. do latency scan
Urim Drift HV Urim GEM HV Beam Current (pA) R1 Rate (Hz) R2 rate (Hz)
3350 3050 0
3350 3050 20
3350 3050 50
3350 3050 80
3350 3050 100
3400 3100 0
3400 3100 20
3400 3100 50
3400 3100 80
3400 3100 100
3450* 3150 0
3450* 3150 20
3450* 3150 50
3450* 3150 80
3450* 3150 100
3500* 3200 0
3500* 3200 20
3500* 3200 50
3500* 3200 80
3500* 3200 1000
  • Watch for sparking on the Trigout pulse and wait 15 minutes after each voltage change so GEM amps have time to reach max gain (charge up capacitor)

Latency Scan

Latency scan procedure.

The steps below describe how to do a latency scan with the R1 electronics by hand assuming the detector is already turned on and operating

1.) Login to the qwgemgumstix computer as root

ssh root@qwgemgumstix

2.) cd to the bin directory

cd bin

3.) type the following commands


If the last command produces error messages call an expert

3.) bring up to VFAT status web page

go to relevant wiki page


click on

R1 Slow Controls computer (qwgemgumstix)

you should see a page with a listing of the 6 VFAT cards in the browser similar to the image below

VFATList 10-8-10.png

There isn't a VFAT card at the link vfat32 (address 32)

You can look at the parameters of each card by clicking on each of the links. You should see an image similar to the one below

VFATRegisterExample 10-8-10.png

The Parameters below should be observed in each of the 6 VFAT card.

VFATParameterValues 10-8-10.png

4.) Now you are ready to take a data run for several latency settings

a.) start a run using the default latency settings( type ~/bin/VFAT.setup in the qwgemgumstix terminal window) and record the value available through the above web interface, clicking on each link will take you to the parameters set for that VFAT card

take at least 1000 events and end the run

b.) Go to the terminal window used to login to the qwgemgumstix and change the latency setting with the following commands

echo "e 16 0 0x0a set" | ./flipbit.arm -n 
echo "e 48 0 0x0a set" | ./flipbit.arm -n 
echo "e 64 0 0x0a set" | ./flipbit.arm -n 
echo "e 80 0 0x0a set" | ./flipbit.arm -n 
echo "e 96 0 0x0a set" | ./flipbit.arm -n 
echo "e 112 0 0x0a set" | ./flipbit.arm -n 

c.) take with at least 1000 events and end the run

d.) repeat c after setting the folowing

echo "e 16 0 0x0b set" | ./flipbit.arm -n 
echo "e 48 0 0x0b set" | ./flipbit.arm -n 
echo "e 64 0 0x0b set" | ./flipbit.arm -n 
echo "e 80 0 0x0b set" | ./flipbit.arm -n 
echo "e 96 0 0x0b set" | ./flipbit.arm -n 
echo "e 112 0 0x0b set" | ./flipbit.arm -n 

e.) repeat c after setting the folowing

echo "e 16 0 0x08 set" | ./flipbit.arm -n 
echo "e 48 0 0x08 set" | ./flipbit.arm -n 
echo "e 64 0 0x08 set" | ./flipbit.arm -n 
echo "e 80 0 0x08 set" | ./flipbit.arm -n 
echo "e 96 0 0x08 set" | ./flipbit.arm -n 
echo "e 112 0 0x08 set" | ./flipbit.arm -n 

5.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x10 set" | ./flipbit.arm
echo "e 48 133 0x10 set" | ./flipbit.arm
echo "e 64 133 0x10 set" | ./flipbit.arm
echo "e 80 133 0x10 set" | ./flipbit.arm
echo "e 96 133 0x10 set" | ./flipbit.arm
echo "e 112 133 0x10 set" | ./flipbit.arm

6.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x20 set" | ./flipbit.arm
echo "e 48 133 0x20 set" | ./flipbit.arm
echo "e 64 133 0x20 set" | ./flipbit.arm
echo "e 80 133 0x20 set" | ./flipbit.arm
echo "e 96 133 0x20 set" | ./flipbit.arm
echo "e 112 133 0x20 set" | ./flipbit.arm

7.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x30 set" | ./flipbit.arm
echo "e 48 133 0x30 set" | ./flipbit.arm
echo "e 64 133 0x30 set" | ./flipbit.arm
echo "e 80 133 0x30 set" | ./flipbit.arm
echo "e 96 133 0x30 set" | ./flipbit.arm
echo "e 112 133 0x30 set" | ./flipbit.arm

8.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x40 set" | ./flipbit.arm
echo "e 48 133 0x40 set" | ./flipbit.arm
echo "e 64 133 0x40 set" | ./flipbit.arm
echo "e 80 133 0x40 set" | ./flipbit.arm
echo "e 96 133 0x40 set" | ./flipbit.arm
echo "e 112 133 0x40 set" | ./flipbit.arm

9.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x50 set" | ./flipbit.arm
echo "e 48 133 0x50 set" | ./flipbit.arm
echo "e 64 133 0x50 set" | ./flipbit.arm
echo "e 80 133 0x50 set" | ./flipbit.arm
echo "e 96 133 0x50 set" | ./flipbit.arm
echo "e 112 133 0x50 set" | ./flipbit.arm

10.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x60 set" | ./flipbit.arm
echo "e 48 133 0x60 set" | ./flipbit.arm
echo "e 64 133 0x60 set" | ./flipbit.arm
echo "e 80 133 0x60 set" | ./flipbit.arm
echo "e 96 133 0x60 set" | ./flipbit.arm
echo "e 112 133 0x60 set" | ./flipbit.arm

11.) Now execute the following commands to change the MSpulse parametera and repeat step 4

echo "e 16 133 0x70 set" | ./flipbit.arm
echo "e 48 133 0x70 set" | ./flipbit.arm
echo "e 64 133 0x70 set" | ./flipbit.arm
echo "e 80 133 0x70 set" | ./flipbit.arm
echo "e 96 133 0x70 set" | ./flipbit.arm
echo "e 112 133 0x70 set" | ./flipbit.arm

Urim Readout Card Map

on 10/2010

Map Map label # Breakout Box label VFAT serial # VFAT Chip ID I2C address
R1 Urim ReadoutCardMap 10-11-10.png 1 D 71 ea c2 80
2 E 73 6a a2 96
3 F 76 71 e0 112
4 C 59 f1 c0 64
5 B 61 f1 c8 48
6 A 83 6a 98 16

Map Map label # Breakout Box label VFAT serial # VFAT Chip ID I2C address
R1 Urim ReadoutCardMap 10-11-10.png 1 D 78 ea dc 80
2 E 74 71 aa 96
3 F 76 71 e0 112
4 C 59 f1 c0 64
5 B 61 f1 c8 48
6 A 83 6a 98 16

V1495 Monitor Pin Out


GEM work summary

5/12/10 : One detector in doghouse with signals, one detector was mounted to double check rotation clearance by hand rotation (break board might hit bolts)

8/19/10: Nauvoo damaged either by beam or mishap on charge collector, charge collector sags more than Urim now

8/24/10: expected cosmic rate measured using Urim

8/30/10 nauvoo working.

9/29/10: Return to find Nauvoo sparking and Urim working

11/14/10: Return to repair Urim , started sparking when Armenian group turned it on

11/22/10: Repaired Urim takes bem and is sensitive to background radiation in Hall C near the G0 patch panel

12/13/10: gas not flowing on Urim but it was working after flowing for 1 day, Nauvoo returned to ISU to fix damage to charge collector