Verlag des Forschungszentrums Jülich
JUEL-2901
Stratmann, Rüdiger
Entwicklung einer Influenzdriftkammer für Experimente an COSY und Untersuchung von Hochrateneffekten nach einem neuartigen Verfahren
110 S., 1994
Abstract
One of the first experiments with the new proton storage ring COSY will be
the measurement of the differential cross-section in the reaction p d ---> 3 He rJ
at threshold. This reaction is known to be of interest due to a surprisingly
large rJ-production cross section. Thus, rJ-production mechanism and decay
features can be studied. Monte-Carlo-Calculations have proved that the
Time-Of-Flight-detector (TOF) is well suited for such measurements with a
good resolution and almost 41r-acceptance (in CMS). The necessary supression
of background reactions will be achieved by using the time-of-flight- and
the ,6.E-information of the scintillator hodoscopes of this apparatus.
In the future, the TOF-detector will be extended by an additional tracking
device with good spatial resolution (o-x ;::;;; 30 JLm) and high rate capability
(~ 106 p/mm2
. s) to improve the angular resolution and to identify secondary
vertices. Such a device, an Induction Drift Chamber, was developed
and has been tested in measurements in Hamburg, Bonn and at CERN (Geneva).
To assure long-term stability of this drift chamber, a detailed study
on the mechanisms of wire-breaking due to sparks Was carried out. Based
on the results of this examination, a new technique for an almost massless
support of the wires with nylon threads was developed, which helped to avoid
breakdowns of the chamber due to destroyed wires.
In the first measurement with COSY the IDC was installed to test its applicabilityas
a high resolution beam monitor and to measure the rate capability
with highly ionizing protons. The IDC shows a good performance and is able
to determine the COSY beam diameter with a resolution of less than 100 JLm.
The use of a Flash-ADC read out of the chamber signals made it possible to
test a new method for an exact measuring of the rate dependency of the gas
gain, even at a low beam rate. At a gas gain of ~ 2.103 the IDC can be used
up to beam rates of at least 2.5.106 particles/mm2
. s (allowing a reduction
in the gas gain of 10 %), which makes this tracking device compatible to the
other components of the TOF-detector.
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