Photocathode Development

A python program has been created which moves the light source (monochronometer) in a square spiral from the Chalice center via the VMX controller. The Keithley electtometer current is recorded and the x,y position is recorded to a logfile.

A 9 point test scan and current vs position map is shown in figure at spiralScan.

Ed May

:: Share or discuss :: 2012-03-26 :: edmay

Programs for VMX Control

Tuesday 20 March 2012 - Filed under Uncategorized

I have completed the first version of some Python based programs to
implement basic operations for the VMX transport motor controller when using the RS232 interface.
They are located in the directory
/home/LAPPD/VMX There is a README file which describes the basic operations.

Currently README contains:
Some Python scripts have be prepared to issue typical command sequences to the
VMX motor controls for common tasks. They are located in the directory
/home/LAPPD/VMX
The bash shell environment is setup with the command:
. setup

Files Description
—————– ——————————————-
VMXmoveDeltaXand.py prompts user for change (delta) of current X,Y position. Enter 0 if
no motion of one position desired. After motion, new X,Y position is
read, displayed and logged to VMX.log

VMXreadCurrentXY.py reads current X,Y position, display to console and logs to VMX.log file.

VMXsingleCommands.py has a menu for online/offline, reset absolute position to 0,0

VMX.log Dated/timestamp log of read back of X,Y position.

e.g.
2012/03/19 18:36:56 -2000.000000 -2203.000000
2012/03/19 18:38:16 203.000000 -2203.000000
2012/03/19 18:39:30 0.000000 -2203.000000

2012/03/19 19:19:45 0.000000 0.000000
2012/03/19 19:21:07 200.000000 500.000000
2012/03/19 19:35:12 200.000000 500.000000
Ed May

:: Share or discuss :: 2012-03-20 :: edmay

electrometer circuit for QE

Sunday 18 March 2012 - Filed under Uncategorized

electrometer circuit for QE

This is a sketch of the circuit used
to readout the current with an electrometer during QE measurement on photocathode deposited on Chalice.

It was found the signal to noise ratio when using the mono-chronometer was poor. The noise level observed in the electrometer was
unacceptably large. It is believed to be the result of poor ground definition and connections. Also the cables between the Chalice pins are long and unshielded. The connections to the Twinax signal pickup and the V-source (coax) are suspect.

Ed May