MiniPrototype CosmicRuns

Cosmic Coincidences

setup

Setup a cosmic coincidence experiment with two crossed scintillators that have the proto-type drift chambers sandwhiched between them.

Built 4 100 ns long delay cables. 2 for the PMTs and one for sense wire 7 on each of the drift chambers.

The top PMT is in channel 7 of the QDC and channel 16 of the scaler.

The Bottom PMT is on channel 8 of the QDC and channel 7 of the scaler.

Coincidence counts are recorded in channel 2 of the scaler.

Runs

Drift Chamber is off

Run 182: Ran with coincidence module in "OR" mode so if either paddle triggered the ADC was read out

Run 183: Switched coincidence module to "AND" mode and ran overnight.

12/23/07

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1500	19
Field	-800	19
Guard	800	0

Run 204: Scope was plugged into DC output (split signal)

12/24/07

Run 206: Unplugged scope and started this run

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1500	19
Field	-800	19
Guard	800	0

I had a bad ribbon cable on plastica. Ignore the results for Plastica. It was just a good pedestal measurement.

It looks like Metalica saw 2/3 of the cosmics seen by the Scintilaltors.

12/27/07

Run 207:

Scope picture of a Cosmic Coincidence event triggered by and AND between the top and bottom scintillator.

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1500
Field	-800
Guard	800

Metalica saw 488 cosmic events while Plastica recorded 494 out of the 739 cosmic events triggered by the scintillator paddles. Assuming [math]\sqrt{N}[/math] counting statistics, I would conclude that the efficiency of Metalica is [math](66 \pm 4)\%[/math] and [math](67 \pm 4)\%[/math] for Plastica when the scintillator paddle is 0.5 cm from the endplate.

12/28/07

Run 208:

Increased Gate width from 200 ns to 1000 ns after realizing that the drift chamber pulses could be that wide. I also removed the 100 ns decay line on sense wire #4 of both chambers. The PMT pulses still have a 100 ns delay line in.

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1500
Field	-800
Guard	800

I saw the ADC peak move up from channel 160 to channel 650 after increasing the gate width. Increase gate width by a factor of 5 and the peak moved up by about a factor of 4.

Metalica saw 922 cosmic events while Plastica recorded 927 out of the 1361 cosmic events triggered by the scintillator paddles. Assuming [math]\sqrt{N}[/math] counting statistics, I would conclude that the efficiency of Metalica is [math](68 \pm 4)\%[/math] and [math](68 \pm 4)\%[/math] for Plastica when the scintillator paddle is 0.5 cm from the endplate. The efficiencies go up to 80% if I include ADC overflow events.

Are the ADC overflow events the result of an ionization event or just large ground line voltage excursions (noise) which were observed on the scope. We couldn't set a threshold on such large noise pulses without blocking the actual drift chamber signal. A correlation plot between the ADC overflow event in the PMTs -vs- the drift chambers showed that only a few (1/1000) events in which both the PMT and the Drift chamber had an ADC overflow.

12/30/07

Run 209:

I increase the HV on both Drift chamber by 50 Volts (25 Volts on guard and Field wires).

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1550	94
Field	-825	93
Guard	825	0

Top PMT is at -962 Volts and the Bottom PMT is at -1036 Volts. The GAS bottle is geting low!

It's on order. The shipment should arrive on Wednesday, 2 Jan 2008. -PLC

Looks like the increase in DC voltage of 50 Volts moved the Peak Mean from 500 to 600 channels.

12/31/07

We have a new bottle of Gas.

Drift Chamber turned on with 90/10 ArCO2 and the voltages below

HV settings
Wire	Volts	current ([math]\mu[/math]A)
Sense	1550	94
Field	-825	93
Guard	825	0

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