Minute of the CDC Group Meeting held on 21-Jun-01 (10:25-12:30 at the Room 425 in the Building No.3)
Japanese version is here
- Date and Place
June 21(Thursday), 2001 at the Room 425 in the Building No.3 (KEK)
- Attendants
M.Kobayashi, K.Fujii, H.Okuno, N.Khalatyan, O.Nitoh, H.Kuroiwa, H.Hashiguchi, T.Hayasaka, M.Araya, Y.Ichizaki, S.Kumano, R.Kuboshima
- Contents
- 1)Cosmic-ray measurement and analysis(H.Kuroiwa)
- 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 this file.(1 page, 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-san's 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..(8 pages, PS 12kB)
- 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.
- 2)Schedule of diffusion measurement(H.Hashiguchi)
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.
- 3)VME-based DAQ system(H.Hashiguchi, M.Araya)
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
- 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.
- 4)dE/dx data analysis(T.Hayasaka)
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.
- 5)Study of the isochrones(S.Kumano)
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. (==>> now preparing)
- *) 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.
- 6)Beam test at PS(M.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.
- 7)Beam test at PS(O.Nitoh)
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.
- 8)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-san.
- *) The next CDC meeting will be held on July 19th (Thu)
from 10:00 at the Room 425 in the Building No.3.
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