Minutes of 50th FFIR/BDSIM meeting on 4/9/2003

The meeting was held in a room of 425 at KEK, 13:30-14:40, 4/9/2003. We discussed on beam profile monitor, FEATHER, dump line and others.

(1) Beamprofile Monitor R&D Based on 3D Sensor (H. Yamamoto, Tohoku university)

(transparencies, 8 pages, pdf ,306KB ) Hitoshi Yamamoto talked on accomplishments in 2002, which are (1) trapezoid 3D sensors fabricated, (2) pixel readout chip prototype designed, fabricated and tested, (3) Tohoku U. Silicon Lab. partially implemented, and (4) one master thesis: Satoshi Tanaka on the pixel readout electronics. There is one graduate student who has been studying the performance of beamprofile monitor. After Tanaka left, a new graduate student (Uneda) was assigned for the readout chip study. A new postdoc will arrive specifically for this project in this summer.

The 3D pixel sensor has been fabricated in a collaboration with University of Hawaii. The sensor has trapezoidal shape, which is 200 um thick, 100 um readout pitch and 3 mm long. It will be tested at the Silicon Laboratory of Tohoku University. The lab. is equipped with Summit 9551U probe station, Kulicke&Soffa manual wire bonder, Agilent 4156c parametric analyzer, and IR laser system ( being implemented).

Pixel readout chip prototype has been also fabricated in collaboration with H.Ikeda (KEK). Designing the electronics circuit by Ikeda and Tanaka, the performance was studied in a frame work of SPICE simulation by Tanaka. The VLSI layout was produced by a company in Hiroshima. The chip was actually fabricated in VEC Rohm 0.35 um process by VDEC (VLSI Design and Education Center, University of Tokyo). It was delivered on January 20,2003, and was tested at Tohoku University. All functions have been verified in terms of pre-amplifier, RC filter, voltage amplifier shaper, sample and hold, 4 samplings in time and pulse height and serial output as a step function. At present, there is no fast gate and threshold in pulse height neither. The chip size is 4 mm2 with 32 readout channels. The size is too large for the proposed beamprofile monitor with 100 um pitched pixels,
Therefore, major issues are the size (channel/0.01mm2) and radiation hardness (~10Mrad) to be studied in future.

(2) Fast feedback system "FEATHER"(N.Delerue, KEK)

(transparencies, 13 pages, pdf ,7.2MB ) First, Nicolas showed a figure of the previous beam test results on kicker-BPM test by re-plotting the BPM signals as a function of location of BPMs. The figure could display the beam deflection in correct timing between the beam and kicker pulse.

He has studied impedance matching of the kicker magnet with various configurations by Poisson calculations. Since we would like to construct a stripline type kicker with movable electrode gap, variations of impedance must be known in details as a function of such movements. The impedance should be close to 50 ohm, He showed many calculations with different geometries of electrodes which are contained in a@cylindrical beam pipe.

Finally, systematics studies were executed for a pair of flat electrodes accompanied each by a wider flat grounded-shield all of which are set in the cylindrical pipe. There are 6 variables in the impedance calculations assuming mirror symmetry between two electrodes, which are length, thickness and position of electrode, length and thickness of shield, and a gap between electrode and shield. He found that the gap and the shield variables do not affect the impedance while the electrode variables can largely change it. An example set of 50 ohm is listed as follows; position from the beam axis, length and thickness of the electrode are 2mm, 9mm long and 1mm thick, respectively, and the gap is 3mm wide. Acceptable range of the impedance could be from 40 to 60 ohm in the 50 ohm system.

He also showed the first order design of kicker with a vacuum chamber.

(3) Discussion on the dump line

We discussed on near future study in terms of the dump line with M.Iwasaki and K.Tanabe (University of Tokyo). First target is to estimate background at IP from the dump line including beam dump. For this purpose, K.Kubo (KEK) is going to design an optics assuming that the horizontal crossing angle is 7 mrad; the beam dump is a water tank of 1.6m diameter, 10m length. The total length of the dump line would be doubled the length up to the second focus point, which is about 300m . Apertures of the beam pipe must be carefully designed along the dump line by detailed simulation. The Tokyo group will calculate the background by the BDSIM based on GEANT4.

The next meeting will be on 23 April (Wed.), 2003,13:30 - 15:00 am at 3 gokan, 325 .