Minutes of 48th FFIR/BDSIM meeting on 3/5/2003

The meeting was held in a room of 425 at KEK, 10:00-11:30, 3/5/2003. We discussed on support tube R&D, FEATHER, beam dump and others.

(1) Support tube R&D (H. Yamaoka, KEK)

(transparencies, 9 pages, pdf ,553KB ) Yamaoka presented the first result of 1/10 prototype support tube. A cantilever consists of four tubes, each of which is 20 cm long and 8 cm in diameter. So total length of the cantilever is 80 cm. The four tubes are connected at flanges each by 12 M6-bolts in the maximum. There are two types of joined portion at the flanges, which are taper and flat. Oscillation property of the cantilever has been studied by hammering method and by ANSYS analysis. The hammered FFT spectrum covers up to about 1 KHz. The oscillation property was analyzed by FRF (Frequency Response Function) which is a ratio of output/input FFT spectrum. The cantilever has nine G-sensors, where each tube has 2 sensors at both ends. Therefore, the oscillation modes were measured up to 5th mode (including 0th). The mode frequencies are listed together with those of ANSYS calculations in a table below, where 0 th-mode corresponds to displacement without deformation;

Measurements and Calculations of Mode Frequencies at the Cantilever
Mode 0 1 2 3 4 5
Measurement (Hz) 57 129 585 1216 1690 2500
Calculation (Hz) - 117 656 755 1916 -
Differences in the above table can be speculated to be due to "goodness" of modeling the support. If the support is assumed to be rigid, the frequency was calculated to be 136 Hz.

He also studied effects of joining strength with different number of bolts in both cases of taper and flat flanges. The strength ranges from 3200 kg (12 bolts) to 800 kg ( 3 bolts), The cantilever joined by flat flanges has smaller frequencies at higher modes especially 4th and 5th-modes with smaller strength, while the one with taper flanges has almost constant frequencies. Therefore, the cantilever with taper flanges is more stable than that with flat flanges as naively expected.

It was pointed out that effects of "heavy load" inside the cantilever must be studied since the actual support tube must contain a quadrupole magnet and heavy masks.

In next fiscal, he will study the case of support tube consisting of two "cantilevers" which are connected by a thin tube.

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

(transparencies, 6 pages, pdf ,800KB ) A meeting was held on 14 February to discuss future plans. Schedule in next fiscal year is summarized as follow; During designing them, beam test will be also performed with available components including amplifier of the kicker, pulse generator and detector-BPM ( cavity BPM). The primary purpose of the beam test is to have experience of real conditions at ATF for the design to which is given first priority. The experiences could be implemented in simulation by MATLAB to optimize the design of the FEATHER system at ATF. However, he encountered problems in the beam test on the 20th February. It was found that a cable to the cavity BPM was not appropriate for this purpose because of its wrong band width. He had a similar problem at previous beam test, which was "too small amplifier power " to kick the beam. So, these problems could be avoided if he had good communication with knowledgeable persons before the beam test. A meeting must be necessary with the "FEATHER" collaboration just before a beam test in order to see if all components are appropriate and available. Everybody in the FFIR group should be encouraged to join the collaboration.

FEATHER home page will be constructed by N.Delerue soon.

(3) Beam Dump and others

We would like to discuss on the basic design of the beam dump and the extraction line at the next meeting. Basic assumptions are that the window size of the beam dump is 15 cm in diameter, there are two windows for beamstrahlung photons and disrupted beam and the crossing angle is 7 mrad. Based on the basic design, we would like to estimate neutron background from the beam dump as well as the extraction line in order to optimize the design.

In April, Hayano-san will review the NLC-design of crab cavity in terms of hardware feasibility.

The next meeting will be on 19 March (Wed.), 2003,10:00 - 12:00 am at 3 gokan, 425 .