Minutes of the BEAST meeting
Friday May 15th

  • Structure:
    Rosen showed a quadrant of the BELLE structure prepared by the Hawaii shop. He will bring a mechanical prototype and retaining ring with him to KEK. The details of the quadrant with Si strips will be finalized when he is in Japan. It was noted that we must check that there is adequate space for cables. The asembly procedure for connecting BEAST to the beampipe and then attaching to the CDC must also be worked out.

  • Simulation:
    Sahu has done further work on understanding the peaks in the z distribution of the e+ bremstrahlung sources. The large sources are associated with bending magnets and in several cases (e.g. BL23RP.3 and BL3RP.5) are associated with the first part of a bending magnet.
    To develop a better intuitive understanding of the sources, Sahu plotted the trajectories of off-energy e+ generated at two locations: s=83 m and s=87 m. The first are particles generated before a bending magnet while the latter are inside the bending magnet. The s=83 m off-energy particles usually hit the vacuum chamber wall far from the IP. About 2% however follow an orbit that passes through the IP without hitting anything. By contrast, a significant fraction of the s=87 m particles hit the wall close to the IP. There were requests for additional checks of particle trajectories for the s= 88 m region and s= 38 m region. Funakoshi promised to compare these results to the SAD calculations as well.
    After the meeting, Sahu plotted trajectories for particles generated at s=88m. These particles are also either swept out far away or pass through the center of the IP. He also traced the trajectories for particles generated at s=35 m which do hit near the IP. Scatterplots of source origin vs energy were also produced to understand another question raised at the meeting: Are all the sources which strike near the IP all off-energy particles with small energy loss ? Answer: No.
    In postscript form, Sahu's plots are on bwg03.kek.jp/~browder/beast/
    e+_brem.ps, e+brem2d.ps, e+brem88r.ps e+bremallz.ps, e+bremallzenergy.ps, e+brem35_35r.ps
    Updated generator information with the new lattice was transferred from Sahu to Bozek.

  • Pressure bump studies:
    The locations of pressure bumps were decided by Kanazawa and Haba. The exact locations should be written down in an e-mail message.

  • Drift tubes and diodes:
    The first 5 PC boards for drift tube readout were received and will be populated and checked. Sanjay Swain (Hawaii student) will start producing proportional tubes.
    On May 19th, the first batch of 100 diodes will arrive. 2 summer students will work on calibration as a function of dose and temperature. A PC board for diode readout was also prepared.
    It was noted that the PC boards for the readout of detector components are 2 meters away from BEAST and mounted in a box on the cryostat. We should therefore check the size of the signals.
    Australian diodes have been tested up to doses of 100 krad
    No news on MOSFETs.
    Still looking for a solid state x-ray detector for observing SR lines. It is probably too expensive to buy one from AMPTEX or other company but there may be one at the photon factory or in the nuclear physics community.

  • DAQ:
    Coordination of DAQ between BEAST and the accelerator is a complicated problem that needs more attention. A list of the quantities to be extracted from the accelerator database will be prepared for the next meeting. Also a list of BEAST measurements to be sent to the accelerator control room will be prepared. These quantities are exchanged in data structures called TDFs (Table Definition Files).