Minute of the CDC Group Meeting held on 21-Jun-01 (10:25-12:30 at the Room 425 in the Building No.3) [I] Reports on the present status 1) Kuroiwa-kun a) He obtained the "attenuation length(L)" for the drift electrons by fitting A*exp(-x/L) to the observed average charge as a function of drift length for several concentrations of oxygen. The attenuation length was then converted to the life time of the electrons using the relation tau = L/v, with v the drift velocity. The attachment frequency (1/tau) for thermal electrons thus obtained was found to be in good agreement with that measured by J.L.Pack and A.V.Phelps, and the measurement by the Mark II people (see Fig.1 ==>> fig1.ps). *) The only thing to be done for the oxygen matter seems to be the calibration of the trace oxygen monitor itself using a zero gas and an 100 ppm span gas (Kobayashi's personal opinion). b) He is now preparing the draft of a NIM paper summarizing the results of a series of cosmic ray tests and the beam test carried out at KEK PS, with the baby chamber. The paper is going to deal mainly with the spatial resolution and the influence of oxygen contamination on it. Click here to see the 0-th version of the draft. c) He and his colleagues are running out of the disk space to be used for the storage of daily accumulated cosmic ray data. *) A SCSI hard disk with a capacity of about 100 GB will be mounted on jlclogin as soon as possible. 3) Hashiguchi-kun He plans to measure the diffusion of a single electron in various chamber gases to accomplish the work of Suzuki-kun (see his master thesis (in Japanese) in the library of our web site). However the chamber currently used can not take sense-wire H.V. high enough to make the wire gain greater than 2.0E5, which is necessary to detect signals produced by one drift electron with the present readout electronics. He suggested two possibilities to overcome this problem: a) replace the detection region constituting of wires with that of a tube-like structure; b) use of a thinner sense wire. *) Limited streamer mode with a thicker sense wire may be another solution. *) It is worth trying on a preamplifier with a higher gain (and low noise). *) It should be noted that the wire gain is not a function of surface field strength alone. For example, under the same surface field a 20 micron wire gives lower gain than a 30 micron wire does. 4) Araya-kun and Hashiguchi-kun Things to do for the new DAQ system: a) Installation of RTlinux on the VME CPU board, which is expected to arrive soon. b) Measurement of the data transfer rate between the CPU board and a PC based on 100BASE-T. c) Preparation of the GUI environment using ROOT. d) Performance assessment of the first VME FADC module which is expected to be completed by the end of June. e) Start (mass-)production of modified (if necessary) FADCs. f) Decision to make between two possible schemes for data transfer: FADC => CPU Board => VME-PCI Interface => PC or FADC => CPU Board => PC. In either case the data compression is carried out by the CPU board. The latter scheme is not necessarily advantageous since the CPU board may become overloaded with two tasks: data collection/compression and communications with the PC. *) The correct name of VME "crate controller" is VME-PCI Interface. *) The data transfer rate within a VME crate (between modules and CPU board) is about 40 Mbytes/sec whereas that between a VME-PCI interface and an external PC is 10 Mbytes/sec. *) For the moment the data-quality monitoring part of the online software is supposed to be based on ROOT. *) Will the new DAQ system be ready for the test experiment in this Fall? Answer: YES. 5) Hayasaka-kun He is trying to evaluate the most probable energy loss by fitting a Gaussian to the region around the peak of the pulse height (integrated charge) distribution for a single sense wire since Landau distribution was found to reproduce the distribution poorly. He found also that the bad quality of the 2-GeV/c proton data, which had been discarded in the analysis by Nakamura-kun, is due to the contamination of pions. He also analyzes the dE/dx data to separate the influence of gas density variations and positive ions on the coordinate measurements and the gas gain. The preliminary result will be presented at the next meeting. *) He had reported a possible bug in the analysis script written by Nakamura-kun. But the script was found to run correctly though it does contain somewhat "risky" lines. 6) Kumano-kun He is looking for an optimum H.V. configuration around the sense wires to obtain smaller dispersion of arrival time of drift electrons. Cosmic ray tracks were collected with the baby chamber with different grid-wire potentials while keeping the sense-wire surface field constant. The preliminary results show the expected change in FWHM of the signal shape. See Fig.2 (==>> XXX.ps). *) Tracks parallel to the sense-wire plane should be selected to see clearly the change in signal shape caused by the H.V. configuration. *) Influence on the spatial resolution should be checked as well. 7) Kobayashi He added the third item to the experimental method in his brief proposal: 1. measurement of tracks created by laser beam with and without uniform irradiation (of various intensities) by particles [laser trigger]. 2. simultaneous measurement of a particle track and a laser track [beam trigger, synchronized laser shot]. 3. feasibility study of the practical calibration using the laser beacon in the beam/laser mixed trigger environment. There has to be at least one laser-trigger event par spill. *) The laser can be excited at a repetition rate of 10 Hz. *) The new DAQ system is expected to be fast enough to take several tens of events during a spill. He also pointed out that we should separate the influence of the temperature/pressure variations and that of positive ions in the analysis of the dE/dx data in order to evaluate to what extent the positive ions alone can affect the global coordinate measurement accuracy. 8) Nitoh-san He has sent in the application for the test experiment at the KEK PS with a title "Study of the space charge effect on the performance of a jet-type chamber". 20 shifts in November are expected to be approved. He stressed the need of a cooperative work by each of group members for the preparation of the experiment. There are certainly a lot of things to do in order to make the experiment successful though the exact date of the experiment is not yet determined. II] Others *) Any proposals, ideas, suggestions are still welcome in order to make the beam time at the PS productive. *) Speakers at the next JPS Meeting in Okinawa: Kuroiwa-kun, Hoshina-san and Kobayashi. *) The next CDC meeting will be held on July 19th (Thu) from 10:00 at the Room 425 in the Building No.3. ====================================