Minutes of A0 photoinjector (local) meeting Friday Jan 30rd, 2004 * Next meeting: Friday February 6th 4pm in "the Motel" * Plan for next week: -Monday: - gun measurements (BPM vs gun gradient + phase scan for various gradients) [Philippe] - look into 9-cell feedback system [Markus] - late afternoon: depending on progress, Matt could run 1 bunch in the plasma experiment area. [BTW: the safety people need to be contacted and informed before doing that] -Tuesday: - cave open, fix/change feethrough of Matt's experiment, stack more lead or move the dump depending on what is decided Monday between Wade, Matt and Kai [Wade & Co + Matt] - laser work, do we need more IR spot size measurements? - install HTBX06 steerer we got from UCLA [Jamie] -Wednesday: - Beam studies (gun and /or 9-cell depending on Monday progress) [Philippe/ Jason] -Thursday & Friday: - Mornings: beam spot sizes measurement [Kai, Jamie] - Afternoons: Plasma experiment [Matt et al.] Discussions: * Achievements of last week: - Monday: - laser studies: some beam spot measurements in the IR, the green and the UV seems to indicate the beam transverse is very distorted (un-uniform) when observed in the UV but is reasonably uniform when observed in the IR, as suspected by few of us, this may mean the problem is in the doubling crystals. [Rodion/Jamie] spot size were recorded [Rodion/Philippe] We know the IR/green crystal as a burn mark but the IR beam is generally steered to avoid this burn mark. Jamie examined the crystal and reported he sees a damaged over the full aperture of the two doubling crystal. These obervations has not been confirmed by somebody else, and a thorough inspection of the crystal is needed before proceeding a buying new BBO crystals - Tuesday: - CTR studies [Daniel/Kai]: a series of autocorrelation measurements were performed for the nominal compression point (22.5 deg bending angle, and 9-cell operated -35 deg off-crest). and other settings around this nominal point. The resulting autocorrelation were very noisy, and the problem, at the end of shift, was tracked to be related to a noisy signal from ICTX8 on the IRM. This ICT is used by the autocorrelation software to record data only when the measured bunch charge is within the value given to the software. - Wednesday: - rf-gun steering [Philippe/Jason] a software to automaticaly scan the gun gradient and record the influence on the BPM1 was tested, results however were very different from previous data taken, e.g. in November. - A diognostics line was setup in the IR laser, to measure the IR beam spot envelope versus distance, this enables the measurement of beam size, waist and thus initial condition at the teslecope entrance (telescope located upstream from the IR-to-green BBO crystal) [Rodion] - Thursday: - CTR studies [Daniel/Kai]: measurements of Tuesday were retaken after M. Kucera fixed the ICT/IRM problem. The autocorrelation looked very nice (quite symmetric), but showed some strange gaps at various location. Data taking proceeded without understanding this problem. After the shift [Philippe], the vector sum phase was monitored for 20 mins and an oscillation with 400 sec period and an amplitude (peak-to-peak) of 3-4 deg was observed, such a phase "jitter" may explain the gaps (due to decoherence of the signal) observed on the autocorrelation signal... - Friday - rf-gun steering studies interrupted time to time with some laser spot measurement [Philippe/Rodion] the position variation on BPM 1 versus gun gradient is still a puzzle. The software was tested, against the the previous WINDOWS-based software, the BPM signal was monitored on the o-scope [Kai] and everything seems alright... - In the evenning some streak camera of the UV laser was performed [Philippe/Rodion] for three bandwidth of the oscillator. For our nominal bandwidth (21 nm) we measured a laser pulse length of 3.5 ps rms * other discussed items: - CTR experiment: Daniel reported on his analysis of his measurement. The autocorrelation obtained Thursday look promising, however taking the Fourier transform of these to compute the power spectrum (in virtue of Winer-Kitchine "theorem"), he obtains a very noisy power spectrum, he cannot presently account for this problem. - Alternative way of getting an idea of gun energy: Philippe reported on measurement of phase scan for various gun gradient. For some gradient (low 10 MV/m ) he observed the phase scan curve start to split into two (there exist injection phases where electrons do an oscillation in the gun before exiting. These measurements are consistent with simulation he showed. [note: such type of observations have been already done by W. Hartung]. Also it is presently hard to use the separation of the two peaks in the phase scan to get an idea of the gun peak field on the cathode -- work still in progress: higher resolution phase scan will be performed. - Laser: Rodion reported on a preliminary analysis done on the laser images. The IR, though it looks uniform, is not perfectly cylindrical symmetric this maybe due to the grating being not properly tuned (?) Altough the latest streak camera measurements tend to kill this hypothesis. It was agreed that before deciding on buying or replacing the BBO crystals (if needed) the spot size evolution downstream of the telescope should be understood and _DOCUMENTED_. ----------------------------------------- * Tasks concerning hardware H2/ Corrector HTBX06, Jamie Steerer from UCLA here, will be installed TUESDAY FEB 3 H8/ calibration of upstream directional coupler and insulator (Markus need to speak to Tim and with Kai to schedule this STATUS?) H11/ Some of the toroid need cabling to have signal available out of the cave in the reack area (JAMIE, STATUS?) H13/ Pulse stacker, what do we do? (Rodion) H14/ air coil steerers, Kai will gather all the paper he has and we will decide whether we can give this project to one of the NIU engineering student (Kai, STATUS: nobody at NIU picked up this project...) H20/ what shall we do with the burnt doubling crystal? Who will specify + order it? (Nick, Rodion and Adrian should discuss next week) 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 efficency? (Rodion/Adrian: Rodion will design and procure a new 4*omega beamline parallel to the present one) H22/ Radiation shielding test: precise plan on what to do and when (Kai + Lautenschlager) H23/ laser spare components list (Jamie, RECEIVED A FIRST VERSION JAN 30, 2004) H24/ cryogenic load test (?)