HM 2014

Long run peak sensing histograms

20min run peak sensing histograms

10/17/14

you need to label the axis and color code the statistics box so I know which distribution corresponds to which configuration.

Date	Shutter	source	run number	Scaler counts (Hz)	pedestal	Integral in ADC full spectrum (Hz)	Integral in ADC spectrum beyond pedestal (Hz)	notes
10/16	Open	off	7847	150+_7	1429/60	7915/60	5810/60
10/16	Closed	off	7846	72+_3	1070/60	4029/60	2817/60
10/16	Open	off	7848	137+_16	19	129	111
10/16	Closed	off	7862	53+_1	7	47	41
10 /16	Open	On	7863	147+_12	30	129	101
10/16	Closed	On	7864	67+_4	15	59	45
10/17	Open	off	7865	132+_14	28	121	97
10/17	Closed	off	7866	95+_7	11	59	49
10 /17	Open	On	7868	150+_6	32	128	100
10/17	Closed	On	7867	74+_4	13	63	52
10/18	Open	off	7872	136+_10	9	124	115
10/18	Closed	off	7871	51+_3	4	48	44
10 /18	Open	On	7869	140+_10	10	123	115
10/18	Closed	On	7870	53+_2	4	49	44
10/19	Open	off	7873	124+_14	10	114	104
10/19	Closed	off	7874	59+_4	5	54	49
10 /19	Open	On	7876	141+_8	10	117	108
10/19	Closed	On	7875	60+_4	6	55	50
10/20	Open	off	7879	129+_16	8	116	108
10/20	Closed	off	7880	49+_2	2	45	42
10 /20	Open	On	7882	142+_3	8	108	99
10/20	Closed	On	7881	53+_2	5	49	44

10/16/14

you need to label these histograms with more detail that will identify the run number and the run conditions.  
Name each histogram according to the run number then in a figure caption identify the run conditions.

you need to show more than just 4 runs, try to take 10, why is the pedestal peak different in the four that you show.

You need to have units of Hz for the count rate on the y-axis.

 I should not be asking you for the above things at this stage of your career, you should be doing hem automatically

 I am not giving any formal results yet since the voltage of the GEM may increase.

The point is to able to understand what is plotted and have a reference to fall back on

 Formal results will be even more detailed 

Last update for the today's measurements

1. Reproduciblity is achieved when for the peak sensing spectra for shutter open and shutter close without source.
2. Increasing the GEm amplification is needed for the case of the shutter open with the source on.

Analyze all runs with same conditions of HV, Gas, … to determine the integral number of counts in the ADC(PADC) histogram that are above the pedestal.

10/14-15/14

Shutter	run numbers	average number of counts above the pedestal
Open	7797, 7802, 7808, 7816
Closed	7798, 7803, 7809, 7817

Fix the percentage plot for the number of betas emitted by the source.

The repcentages do not add to 100% according to two different references.[1][2] they add to about 20%, the first referece bentioned that the average energy for the emitted particles from U-233 are

Ebeta (eV) : 5.043230e+3 (5.363190e+2)

Egamma (eV) : 1.110210e+3 (1.076780e+2)

Ealpha (eV) : 4.888350e+6 (2.896760e+4)

Fix the alpha log plot for cross-section, change units on the beta plot for cross section so they are in barns.

Add plot for expected voltage on oscilloscope.

Alpha
Beta		[3]
Gamma			300 px

10/13/14

stripchart

Relationship between barns and g/cm^2

[math] macroscopic \,\, xsection (cm^2/g) = \frac{6.022 \times 10^{23}}{atomic mass} * xsections \,\, (cm^2)) [/math]

paragraph describing percentage plots for alpha, beta, and gamma with references.

long run	time	shutter	source	Notes
7832	6h	open	off	8dB
7834	35min	closed	off	8dB
7836	5.5h	open	on	11 dB

10/02/14

QDC's and Peak sensing's spectra distinguish between shutter open and shutter close as the source is on, I noticed it from yesterday's and today's measurements.

Also the spectra shows a difference in the number of count and the number of channels as the source on or off as the shutter is open. more measurements is needed to calculate the STDEV.

The oscilloscope picture is shows the gate and signal details,

date	time run ended	Source	run number	notes
10/02/14	10:45	On	7792	each run time is 20 min.
10/02/14	11:07	off	7793	22', taking the source off directly then measuring the charge does not show any difference in channel number but shows difference in counts.
10/02/14	16:30	off	7795	20', after 5 1/2 h the detector started to show a little difference again between shutter open source is on and when the source is off.
10/03/14	8:00	off	7795	20'
10/03/14	11:21	off	7795	20' equilibrium without source.
10/06/14	09:05	off	7802	20' equilibrium without source.
10/07/14	7:00	off	7806	lower charge is detected
10/07/14	11:19	off	7807	higher charge is detected (TSO's stuff were checking on the source)

GEM_HV= 2870 Volts, Drift HV = 3470 Volts

09/30/14

Plot of shutter open/closed (NO SOURCE) counter rate -vs- date

Alpha's Primaries

File:Alpha primaries.xls

Plot of Number of electrons collected -vs- Energy of (alpha, beta, and gamma) from U-233

Electrons

[K Paludan et al 1997 J. Phys. B: At. Mol. Opt. Phys. 30 L581 doi:10.1088/0953-4075/30/17/005 ]

link title

Gamma

300 px

09/29/14

Shutter open/close data plot for 2.87 3.48 kV GEM /Cathode

[4] The reference gives percentages of the emitted alpha particles as U-233 -> Th229 File:Alpha percentages.txt

Roy's detector infomation and measurements

U-233 metal deposited source is measured by Protean Instrument corporation gaseous detector, has a model number of WPC9450 (serial number: 0915723)and uses (P10) gas mixture, as shown below:

Shutter position	Alpha particles /min.	Beta particles /min.
Open	6879	900
Close	1	38

09/20/14

Rate of ( alpha, photon, beta) -vs- energy for U-233

Primary electron ionization -vs- (alpha,photon, beta) energy

Alpha Secondaries

Photo-Absorption Secondaries

The reason that the graph started from 30 keV is the lowest gamma energy emitted by U-233 or Cf-252 is higher than that energy.

Electron Ionization

Using NIST data base [5]

we got the following data file for CO2 File:CO2 e ionization xsection.txt, For Ar, the ref. [6] that measured the ionization xsection.

09/20/14

The figure below shows the change in the signal as the GEM capacitor charges, at a specific fixed voltage it reaches saturation (equilibrium),

If the capacitor does not reach equilibrium, the signal of the detector is expected to change with time.

 What may forbid the GEM capacitor to reach the equilibrium?

1. The circuit board voltage fluctuations.
2. The following reference describes almost the same conditions as those of our detector when their detector is in operation to detect simultaneously photons with alpha particles.

Nuclear Instruments and Methods in Physics Research A 471 (2001) 151–155

File:Gas electron multiplier for portal imaging wallmark.pdf

The author commented in the conclusion "The studies show that GEMs can operate at extremely high rates (>10^6 Hz/mm^2) with no sign of degradation and stability loss due to radiation damage. However, it was discovered that the maximum achievable gain for all planar gaseous detectors drops with the beam intensity "

"In real clinical operation the detector can operate safely with a gain of 10^2 in the GEM closest to the collector".

 Our detector has a rate of 100-170 Hz (without and with the source), considering  the detector age, will this rate cause an instability?

1. High detector rate.

File:Fonte GD limitations.pdf

The gain will decrease when the count rate increases, if GEMs' voltage is at the point where gain is stable with the high rate, the detector output will be reproducible. As mentioned above, a gain of 10^2 made it enough for imaging with a well-quenched gas, I doubt we need to increase the gain more than that.

9/18/14

Determine best Cathode HV that produces the largest separation of the source ON/OFF signal.

The detector results are not reproducible, as the voltage is at 3.4 kV, the QDC spectrum is different as the source on; so QDC can not distinguish if the source is on or when it is off the detector.

Something is wrong!!!!

We never have a reproducibility problem before using the QDC until I start using V1495, Can we borrow the older module just to test the reproducibility is still a problem.

It is very unlikely that it is the v1495.  The V1495 only tells the DAQ to read out a module.  
You can test the DAQ by injecting a pulse with a known charge and look for it in the QDC spectrum.

It is VERY important to have scope pictures showing the difference between source ON/OFF.
Then you use scalers to check that your trigger pulse is able to see a difference between source ON/OFF
Then you do the DAQ measurements.  

If you don't follow the above proceedure then you will be building a pyramid on quicksand.

The same case when the cathode voltage increased to 3.6 kV.

Then perform a set of measurements (shutter open/closed and source ON/OFF) to establish reproduceability. Make sure you record the scaler count rates.

9/17/14

Measure the charge for several values of the Cathode HV keeping the GEM preamplifier voltage and gas flow rate constant.

CATH 3.2 KV

CATH 3.1 KV

All the runs have the same duration 20 min.

CATH 3.4 KV

Try to take scope picture to show difference between source on and off signal that are being measured by the QDC.

9/16/14

Condition of above results

Shutter is Open

Red is Cf-252 source ON Run 7724

Green is Cf-252 source OFF run 7726

HV_GEM= -2930 Volts HV_Cathode=-3400 Volts

Gas Flow rate = 0.1 ft^3/hr

Goal

Can the Cf-252 source ON signal be changed?

Change the Cathode voltage to try and turn off the signal when the source is on.

Result

Yes, when the cathode voltage is decreased to -3100V, QDC histogram does not show any difference in the collected charge as the shutter is open with the source on it, and when the shutter is open without the source.

The figure below shows the change in the QDC spectrum when the cathode voltage is -3.2 kV.

Neutron_TGEM_Detector_Abdel