IAC 2-29-08

DC setup

This time the Sense wire HV is set to 1500 to start

90/10 ArCo2

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1500
Field	-750
Guard	750

DC preamp at 5.6 Volts

Beam Line Configuration

A 1/4 inch diameter collimater is placed in the experimental cell just after a Helium bag inserted in the wall. A 2 cm thick scintillator is place over the beam downstream side of the collimator aligned using a laser. A 3mm diameter collimator is placed just before a 1 kG magnet that is after the DC. The 1 kG magnet placed after the drift chambers deflects charged particles onto a large scintillator paddle.

A logic circuit was wet up to allow for the following trigger configurations

1. gun AND (Front Scint OR Rear Scint)
2. gun AND (Front Scint AND Rear Scint)

Increased beam energy from 10 MeV to 12 MeV due to expected energy loss in front scintillator.

Data was taken with the

1. gun AND (Front Scint OR Rear Scint)

trigger. The back scintillator output is in the data stream (ADC14 in C-convention, ADC15 in ntuple) so A software coincidence will be used. The rate with ANDing all signals was time prohibitive.

Runs

A

Decided to increase beam current until up to 10% of events in front scintilaltor pass through magnet after drift chamber and hit back scintillator. Ran in OR mode so a software coincidence can be formed based on measurement in ADC15 (ADC14 in C convention).

Run #	Description
431	0" from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
432	0" from feedthrough , Sense wire at 1500 Volts, Metalica (ADC6; C-convention) sees overflows and looks hot on scope compared to Plastika (ADC8: in ntuples),Gun voltage at 1.76
433	-1" from feedthrough (beam should miss chamber), Sense wire at 1500 Volts, I see peds in Plastika but not metalica (Metalica is beam upstream of Plastika), The overflows are due to DC voltage/Gain being too high ,Gun voltage at 1.76
434	1" from feedthrough , Sense wire at 1500 Volts, Gun voltage at 1.76
435	2" from feedthrough , Sense wire at 1500 Volts, Gun voltage at 1.76

B

Change voltage on DC to values used on last day of January run 90/10 ArCo2

Drift Chamber HV

HV settings
Cable #	Volts	Current (ma)
Sense	+1450
Field	-725
Guard	+725
Front Scint	-1127	30 mV threshold
Rear Scint	-1153	81 mV Threshold

Run #	Scint counts > 70 channels (ADC15)	Scint counts/trigger	Description
436			2" (-100k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76, Less overflows in Metalica ADC
437			4" (-200k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
438			1" (-50k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76, visually inspected position and confirmed it was 1" from feedthrough
439			0.5" (-25k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
440			0.25" (-12.5k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
441			0.0625" (-9.375k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
442			-5" (+240.625k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76, try to get electrons missing chamber, use ADC14 to cut on electrons hitting back scintillator. ADC7 should be zero if its really an electron.
443			-3" (+140.625k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
444			-2" (+90.625k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
445			-0.5" (+15.625k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
446			-0.25" (+3.125k) from feedthrough , Sense wire at 1450 Volts, Gun voltage at 1.76
447			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply On, Preamp Power supply at 5.6 V, trigger: gun OR either scintillator
448			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off
449			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off, DC preamp off
450			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off, DC pramp off, Now just trigger on gun pulse, DC HV off

Run #	r436	r437	r438	r439	r440	r441	r442	r443	r444	r445	r446
Distance(inch)	2"	4"	1"	0.5"	0.25"	0.0625"	-5"	-3"	-2"	-0.5	-0.25"
ADC15
3	100px
4	100px
5	100px
6	100px
7	100px
8	100px
9	100px
10	100px
11	100px
12	100px

Distance(inch)
2"
4"
1"
0.5"
0.25"
0.0625"
-5"
-3"
-2"
-0.5"
-0.25"

Rear Scint Pedestal

Run #	Scint Histogram	Wire #4	Description
447			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply On, Preamp Power supply at 5.6 V, trigger: gun OR either scintillator
448			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off
449			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off, DC preamp off
450			Beam turned off, Pedestal run, Sense wire at 1450 Volts, Translator Power supply Off, DC preamp off, Now just trigger on gun pulse, DC HV off

Observations

The pedestal for the last scintilator is below channel 70. There seems to be a lot of noise around channel 150.

turning the DC amplifier off increases the noise on the line (no more differential amplification).

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