Joint PSP/Taskforce minutes for 05 Dec 2019 ============================ http://beamdocs.fnal.gov/AD-public/DocDB/ShowDocument?docid=7851 (a) Updates from Tan for both PS and Task force (i) Status of PSP projects (1) H- test stand is up and running. Normal magnetron has been installed and some beam has been extracted. (2) Laser collimation. New style flange has been designed. Waiting for quote. (3) Flat injection porch. Studies done on 27 Nov with DC ramp. Analysis ongoing. (4) Wide bore cavity. To be tested soon. (5) Garnet loss improvements. Meeting on 02 Dec. Waiting for mechanical engineer to be assigned. (6) GMPS. See today's talk on Bdot circuits. (7) Digital paraphase module. Getting close. Need one more knob to tune. Ready for next set of dedicated studies. (iii) Task force (1) Tall aperture gradient extraction magnets. Calculation of gap size is complete. Will meet on 11 Dec to discuss. (2) 20 Hz cavity test. Report is being written. (3) 50 kV in situ cavity test which is required for PIPII. Plan is to test in January. (b) Kent gave a bdot study report (1) Kent showed that nothing is rock solid when the injection pulse is measured w.r.t. IMIN. (i) the line frequency is continually changing (ii) the 15 Hz line frequency is changing. (iii) HIstorically, the jitter is about 40 us. (2) Various methods have been looked at to replace Bdot IMIN (i) voltage dividers. (ii) pickup coils placed along the bus (iii) Rogowski coil around the bus. (3) The existing Bdot detection coil in the reference magnet is simple and very robust. (i) Bdot is used to detect IMIN because it goes quickly through zero volts at the moment which allows fro precise timing. (4) Original system detects the Bdot zero and then uses a fixed time delay for the Booster reset. (i) The delay is not really fixed because the clock breathes with the line frequency. Jitter is about 40 us w.r.t. to Bdot zero. (5) First attempt to reduce the jitter used BMAX to cut the time delay by 1/2. But this did not improve the jitter. (6) Bill built a crystal based clock that averages the time between 2 Bdots to generate the Booster reset. (i) This method reduced jitter to 6 us. SOLVED! (7) Magnet voltage dividers were evaluated as a replacement for the Bdot signal (i) Both amplified and unamplified signals were evaluated. (ii) Both systems were affected by RF which made the signals very noisy. (iii) There was also drift of the zero crossing signal that was not correlated to the line frequency. Triggering was made by triggering scope on previous Bdot. (8) Home made magnetic pickup coil was also used. (i) Filtering removed RF noise (ii) However, there are kinks in the signal after filtering. Looks like gated RF is still seen. (9) Rogowski coil measures Idot which is like Bdot (i) Also has RF noise. (ii) However should be able to be filtered out. (10) Booster is the only synchrotron that does not have damping resistors. (i) Problem with adding damping resistors is the reference magnet which needs the addition of inductance. (ii) Howie says that without the damping resistors, transmission line modes can be induced by unbalanced PSs (a) Historically, new GMPS caused 200 Hz mode because of rise time difference between GMPS PS. (b) Simulations show that PS that have mismatched rise times can cause these modes. This problem has been seen 3 times. (c) One time was mismatched rise time of trapezoidal waveforms. Tuned rise times of all the PSs to match rise time. (d) Changed trapezoid to sine to reduce higher order modes. (e) Second time may be something Bill did. (f) third time was MOSFET not firing correctly in one of the PSs. Tightened down connections fixed problem. (10) Plan is to use Rogowski coil (i) Add filter to remove noise. Expected jitter is 10 us. (ii) Short out reference magnet and use Rogowski coil to generate Bdot. (iii) If Rogowski coil works. Add in damping resistors. (11) PIPII consideration: Addition of new 2 extraction and injection D magnets might cause problems. This needs to be simulated in SPICE model. Howie says that Dan Wolf is willing to do the simulations once we get more details of the new magnets.