We had the 4th IP-BPM meeting at 15:30-17:00, 20th June 2006, 425, 3-gokan, KEK.

Participants: P.Doublet, Y.Honda, T.Hino and T. Tauchi

Philippe reported his work for last two weeks. His presentation is here.

Following Alexey's suggestion to use symmetry for reduction of total mesh number, a quadrant of IP-BPM has been studied by MAFIA. He could not define symmetries properly in MAFIA. Another trial has been made by re-scaling the geometry by 1x106 times for nano-meter resolution. It turned out that this method does not help the nanometer-scale calculation since the MAFIA works with ratios between distances, i.e. relative length as other simulation codes.

Tolerances of the cavity dimension has been studied by using MAFIA. First study was the quality factors. of . The design values are Qx=5300 and Qy=4900 at a=61,4mm and b=48.56mm, respectively, while these calculated values are slightly larger. Their variation is about 1% within the dimensional change of Δa, Δb=±2.5mm, while they vary linearly as a function of a and b. Next study was the dipole frequencies, which are 5,712MHz and 6,426MHz in x and y directions, respectively. The frequency change was measured to be 200MHz/5mm, that is 10MHz/250μm for the electronics requirement. These results show the mechanical tolerances.

The electronics studies have been conducted for phase isolation, noise study, phase differences and tests with pulses. (1) Phase isolation : The phase was adjusted at the maximum input voltage in the beginning, where the inputs were decreased at the RF generator. Outputs with 0o phase have been measured as a function of ones with 90o at four different setups. An oscillating phenomena have been observed. It was speculated that the limiter could make them, since the reference signals also varied as the sensor ones. (2) Noise study : S/N has been measured as a function of the input voltage, where "the noise" was constant at 740mV. It was pointed out that this noise was not right. (3) The phase difference has been measured as a function of the input voltage as suggested in the previous meeting. (4) Tests with pulses which are simulated ones as the beam signals.

Suggestions are listed below;

  1. In measurement of phase isolation, the limiter input signals must be constant as real condition.
  2. Noise study should be instructed by Honda-san. An example can be seen in this figure which has been investigated in the SLAC electronics of QBPMs.
  3. Results of the phase difference should be consistent with those of the phase isolation. So, the data analysis can be made.
In addition, his homework is listed below, as he asked.
  1. New design for the ILC beam with bunch length of 300μm while the ATF2 beam has 8mm bunch length.
  2. Noise study with Honda as listed above.
  3. Notes of the beam tests.

We will have the next meeting on 4th July 2006.