Minutes of A0 photoinjector group meeting
                        Friday Nov 19 th, 2004


     
      minutes at: http://nicadd.niu.edu/fnpl/Operation/Minutes/



* Plan for next week:

    - Monday, Tuesday and Wednesday will be splitted between 
      HOM, laser sutdy and gun measurement (QE, dark current and 
      BBA)
    - Starting Tuesday at lunch time, the TESLA cavity will be 
      warmed up
* plan for after thankgiving week-end:
    -Monday/Tuesday Walter will be visitin and doing, with Ray, 
     measurement on dark current and quantum efficiency. 
     
    
* Last week activity

- We had a lot of trouble with the 92 tons chiller (the chiller 
  failed several times but it now appear to be fixed)
- The chiller failure prevented us from running the beam, and even 
  the laser, since the 2-pass amplifier is cooling depend on the 
  62 tons chiller 

* Discussion
- Rodion and Jianliang reported on their visit at the APS LEUTL 
photocathode drive-laser. The laser is from the same vendor we 
are buying our new oscillator (Time bandwidth) but the medium is 
glass (we are getting a YLF). The laser generate shorter pule than 
us (2-3 ps in the IR) and the frequency quadrupling seems to be 
easier (thinner crystal for 15 % conversion efficiency -- we are 
getting only 3-4 %). The APS person (Yuelin Li) told the laser 
transverse uniformity is very good, and the cntensity fluctuation 
is typically 2 % (rms). Jianliang and Rodion did some vibration 
measurement, and similarly to their observation at the AWA laser 
room in Argonne, they find the vibration level is 3-4 times smaller 
that the level measured in the A0 building. 
- We do not consider anymore asking for the IQ laser company to 
come to give us a demo of their laser. It seems the general agreement 
is to try to get the time-bandwidth oscillator (it is now in the procuring 
phase at NIU)

- Tim and Jacek Sekutovicz (DESY) did some HOM measurement. Jacek confirmed 
the fear from Tim: the signal we observed from the connectors outside of the 
cryostat are not characteristic of the HOM coupler spectrum response. It 
looks like the cable are unplugged in the cryostat. Such a finding kills 
our hope to do HOM-based alignement of the beam (at least for now)



plan for next week:


ACTION ITEM updated:
Thu Oct 1st 16:07:11 CDT 2004

H8/ calibration of upstream directional coupler and
    insulator (Markus need to speak to Tim and with Kai to
    schedule this STATUS?)
H13/ Pulse stacker, what do we do? (Rodion)
H21/ the laser uniformity problem can this be due to the new (since
     late summer) tight focusing in the doubling crystal area to
     improve conversion efficiency? On going work [Rodion]
H28/ Problem with emittance measurement at X7 (Philippe 04/16/04)
H32/ Digital camera from SONY(?): [Philippe/Yin-e]
     to be TESTED with OTR [Sep 27]
H33/ laser fluctuation since June 1st week [FIXED?]
H34/ Need more work on power supply + devise a way to measure
     the current being put out to the magnet [Jamie]
H35/ A0 cryosystem contamination
H36/ laser room/table vibration studies


#.36

from Adrian Melissinos:

NEEDED LASER STUDIES:

1. Study of oscillator bandwidth versus length of
   compressed pulse. Measure IR length using stepping
   autocorrelator [Done week of AUG 23rfd 2004]
2. beam profile (wavefront) studies both in IR and UV
   in laser room and on virtual cathode. Use spatial filters
3. study of doubling and quadrupling efficencies with old
   and new crystal, take a tuning curve

POSSIBLE LASER UPGRADE PROJECTS

1. Measure IR pulse length before compression (use diode?)
   implement cw autocorrelation
2. Install new beamline between multipass and 2-pass --
   install spatial filter, rebalance 2-pass amplifiers
3. Relay imaging UV from laser room to cave
4. _harware_: replacing all coolers with new system IV +
   use existing system III as back-up
5. pulse stacker studies, new pulse stacker R&D