[Tgun] GTS Photogun Beam Structure

[Riad Suleiman]

Hello,

These are the GTS beam structures used with the photogun:

1. CW Beam for high current runs: Micro structure of 374.25 MHz, 50 ps.

2. Tune Beam for Harp: Macro structure of 60 Hz, 250 us. The nominal 
average beam current during a harp scan is 100 nA. This gives a peak 
current during the 250 us of about 0.1*1/(60*0.000250) = 6.7 uA.

3. Viewer Limited Beam for Viewers (YAG): Macro structure of 60 Hz, 4 
us. The nominal average beam current on viewer is 2 nA. This gives a 
peak current during the 4 us of about 0.002*1/(60*0.000004) = 8.3 uA.

Notes:
1. We use a Beam Sync signal that goes to the laser table to generate 
the beam macro structure. This signal also goes to the harp to trigger 
the readout. Another copy goes to the camera of the third viewer. Of the 
three viewers, only the third one has a camera with an external trigger. 
We are planning to run at 10 Hz this summer and will find out if there 
is any issues related to running at frequencies other than 60 Hz.

2. The Harp ADC records only one sample at approximately the middle 
point of the 250 us beam pulse. Thus, reducing the width of the Tune 
Beam may require other changes to Harp readout.

Yours,
Riad.

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