Mini-prototype

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Drift Chamber prototypes were constructed to evaluate drift chamber designs for CLAS12 MiniPrototypeWirePattern.jpg

Mini-prototype Performance Measurements

Description of General Operation

Chamber Ionization Gas

Our initial plan will be to use [math]ArCO_2[/math] (75/25) flowing though the chamber at a flow rate high enough to exchange the volume once a day.

high Voltage supply

A CAEN 4 channel high voltage supply (N470) will be used to supply HV to the drift chambers. The supply is capable of monitoring currents at the microAmp([math]\mu[/math]A) level and voltages at the Volt (V) level.

Signal Processing

Eelectronics.jpg
The output signals from the drift chamber will be processed through several NIM based modules.

Dan or Phil:  Insert specs of amplifier needed to see DC signals

A descriminator from Lecroy whith a threshold range from 30 mV up to 1.5 Volts will be used to create a stop pulse for TDCs that are started by scintillators which detect either an electron, during tests at the IAC, or cosmic rays, during tests at the LDS (see below). Hall B has loaded the ISU group a TDC module for the drift chamber studies. Pulse height studies may also be done using an ADC. The DAQ system to manage the signal processing electronics is described below.

DAQ System

The DAQ system is described here

Cosmic tests

Apparatus

Place chamber between two plastic scintillator paddles to check signals.

scope pulses

Planned tests

Electron test facility

IAC 25 MeV electron accelerator

The Idaho Accelerator Center (IAC) operates a 25 MeV Linac capable of delivering instantaneous electron currents of 80 mA/pulse. Pulse widths range from 80 ns to 2 [math]\mu[/math]s and repetition rates from single shot to 1 kHz. Drift Chamber testing will use this accelerator to create a secondary electron beam as described below.

secondary electron beam setup

Description of collimation system goes here as well as lead pencil target. Description of how beam size will be measured or why it isn't needed.

stepper device

Drift Chamber efficiency measurements

Efficiency -vs- Distance

The results of our tests will be placed below.

Plastic feedthrough

Metal feedthrough