Monday, March 11, 2002 - DPG-Tagungen

Nuclear Physics Tuesday
In this talk we discuss the possible application of new reconstruction
techniques in nuclear physics experiments. Furthermore the problem of
generalisation and implementation in other fields such as medical imaging
will be discussed. As an application we present the status of ongoing
work with planar low energy x-ray images obtained at small stereo angles.
HK 14.24 Tue 10:30 Foyer Chemie
Performance of the CERES TPC — •H. Appelshaeuser 1 and A.
Marin 2 for the CEREScollaboration — 1 Physikalisches Institut der
Universität Heidelberg — 2 Gesellschaft für Schwerionenforschung mbH
In 1998 the CERESspectrometer was upgraded by the addition of
a large cylindrical Time Projection Chamber (TPC) operated inside
the field of a new magnet system to provide momentum measurement.
Key issue is the improvement in mass resolution in the ρ/ω/φ region to
∆m/m < 2%. The TPC adds also to the electron identification capability
via dE/dx. Furthermore, the TPC opens the possibility of reconstructing
the φ meson through its K + K − decay channel.
The operation of a radial drift TPC inside an inhomogeneous magnetic
field requires a very detailed understanding of the underlying electric and
magnetic field configurations, drift properties for the Ne:CO2 (80:20) gas
mixture, and detector geometry. We present the status of the TPC calibration
and discuss the present performance.
HK 14.25 Tue 10:30 Foyer Chemie
Laboratory High Speed DAQ — •F. Karstens, A. Danasino, H.
Fischer, J. Franz, A. Günemeier, S. Hedicke, F.H. Heinsius,
M. v. Hodenberg, W. Kastaun, K. Königsmann, J. Reymann,
T. Schmidt, H. Schmitt, andJ. Worch —Fakultät für Physik der
Universität Freiburg, Hermann-Herder-Str. 3, D-79104 Freiburg.
Hitherto data acquisition systems in laboratories were characterized by
flexible setups, but slow data rates. High data rates are mainly realized
in fixed setups at large accelerator experiments. This poster presents a
solution, which involves both - high data rates and flexible usability.
The DAQ of the COMPASS-Experiment at CERN has been adapted
for laboratory purpose with two additional modules - a trigger-logiccontroller
and a trigger-distributor - substituting the sophisticated trigger
system. In our system trigger signals are generated by a programmable
combinatoric logic in a VME-module using modern FPGA technology.
Alternatively the module can be used as a programmable prescaler. The
second module, realized in NIM-standard, provides a fan out for the trigger
signals and the experiment clock. It interfaces to the existing DAQ,
in particular to the Freiburg CATCH-module.
The DAQ system is scalable and conveniently adjustable to different
inputs due to exchangeable mezzanine cards, what makes it interesting
for a variety of experiments.
For further information:
http://hpfr02.physik.uni-freiburg.de/projects/compass/electronics
This project is supported by BMBF.
HK 14.26 Tue 10:30 Foyer Chemie
Development of the ALICE TRD Radiator — •Damian Bucher
for the ALICE-TRD collaboration — Institut für Kernphysik, Westfälische
Wilhelms-Universität, Münster, Germany
In this poster we present the design and tests of the radiator for the
ALICE Transition Radiation Detector (TRD). The ALICE TRD consists
of 540 individual detector modules which cover an overall area of about
750 m 2 . Individual modules, which consist out of a radiator followed by
a drift chamber, have entrance windows with a maximum size of about
1.2 ∗ 1.6 m 2 which are covered by the radiators.
The radiator for this detector not only has to give a very good transition
radiation yield but also acts as one of the main mechanical supporting
structures of the detector modules. The crucial goal is to keep
the entrance windows, which serve as the cathodes of the drift chambers,
within the tolerated deflection of 1 mm.
To achieve this, various materials were evaluated during several test
beamtimes and checked for their mechanical properties. The requirements
for the radiator resulting from the detector design as well as the
final foam/fibre sandwich construction are presented.
HK 14.27 Tue 10:30 Foyer Chemie
A new Data Acquisition System for COSY TOF ∗ — •A. Erhardt
1 , M. Drochner 2 , T. Sefzick 2 ,andP. Wuestner 2 for the
COSY-TOF collaboration — 1 Physikalisches Institut der Universität
Tübingen — 2 Forschungszentrum Jülich
Driven by the need for a faster data acquisition and implementation
of the delayed-pulse technique for π + identification by use of multihit
TDCs, the TOF collaboration decided to build a new data acquisition
system. The experiment messaging system (EMS) has been chosen for
several reasons: The system is successfully in use at several other experiments
at COSY and the know-how is nearby since the system has been
designed by people working at the Forschungszentrum Jülich. The new
DAQ has been installed before the August 2001 beamtime and has been
successfully used in that beamtime. This contribution shows how the different
components cooperate, how compatibility with the collaborations’
data analysis demands will be assured, and which further developments
are planned. ∗ supported by BMBF (06 TÜ 987) and DFG (European
Graduate School)
HK 14.28 Tue 10:30 Foyer Chemie
LED-Flashers for the TOF detectors — •I. Martin, P. Grabmayr,
T. Hehl, andJ. Heim — Physikalisches Institut, Univ. Tübingen
For the detection of neutrons at intermediate energies the time-of-flight
method employing fast scintillation counters is the only one which provides
sufficient resolution for precision studies. A pulser system with
Light Emitting Diodes has been developed for calibration, adjustment
and surveillance during data taking. This system has been improved
recently with blue ultra-bright LEDs. The electronic and mechanical redesign
will be presented. Results from bench test will be shown as well as
the performance during data taking at the (γ,NN) experiments at MAMI
will be discussed.
[1] T. Hehl al., Nucl. Instr. Meth. A354 (1995) 505
This work is supported by the DFG (European Graduate School Basel-
Tübingen and SPP 1034)
HK 14.29 Tue 10:30 Foyer Chemie
The Nuclear Polarization of Molecules from Recombined
Polarized Hydrogen and Deuterium Gas Atoms — •Hellmut
Seyfarth 1 , Ralf Engels 2 , Peter Kravtsov 3 , Bernd Lorentz 1 ,
Maxim Mikirtytchiants 1,3 , Hans Paetz gen. Schieck 2 , Frank
Rathmann 1 , Hans Ströher 1 , Nikolay Tchernov 3 ,andAlexandre
Vassiliev 3 — 1 Institut für Kernphysik, Forschungszentrum Jülich,
52425 Jülich, Germany — 2 Institut für Kernphysik, Universität zu
Köln, 50937 Köln, Germany — 3 High Energy Physics Department, St.
Petersburg Nuclear Physics Institute, 188300 Gatchina, Russia
During the past decade, polarized atomic H and D storage-cell gas
targets have been successfully applied at storage rings. However, a fraction
of the polarized atoms recombines in wall collisions. The nuclear
polarization, of the molecules is not directly accessible with a Breit-Rabi
polarimeter (as used at HERMES), only the polarization of the atoms
extracted from the cell can be measured. In order to overcome the resulting
systematic uncertainty in the total overall nuclear polarization
of the target gas, the nuclear polarization of recombined H2 molecules
was recently studied in a separate experiment [1]. A high value has been
found for a strong external magnetic holding field. In the framework of
an ISTC project [2], additional investigations of polarized hydrogen and
new studies of polarized deuterium molecules are being prepared. These
will also include different hyperfine state compositions and variation of
the storing conditions like material and dimensions of the cell walls.
[1] T. Wise et al., Phys. Rev. Lett. 87, 042701 (2001).
[2] International Science and Technology Center, project no. 1861.
HK 14.30 Tue 10:30 Foyer Chemie
Study of the liquid hydrogen jet properties at the ANKE pellet
target — •P. Fedorets 1 , V. Balanutsa 1 , W. Borgs 2 , M.
Büscher 2 , A. Bukharov 3 , V. Chernetsky 1 , V. Chernyshov 1 ,
M. Chumakov 1 , A. Gerasimov 1 , V. Goryachev 1 , L. Gusev 1 , Z.
Khorguashvili 4 , and S. Podchasky 1 for the ANKE collaboration
— 1 ITEP, Moscow — 2 Forschungszentrum Jülich — 3 MPEI, Moscow —
4 IPH GAS, Tbilisi
A pellet target will be utilized at the ANKE spectrometer to reach
highest luminosities with a hydrogen pellet jet crossing the stored, circulating
COSY beam. One of the main experimental tasks is to produce
a stable liquid hydrogen jet, which will further be broken into microdroplets
of about 50 µm diameter by acoustic excitation and finally freeze
into pellets. Special care has to be taken about the jet-production boundary
conditions. For this purpose jet modifications close to the triple-point
(T =14K,p = 100 mbar) were studied, since only there stable jet can
be generated. The status of the ANKE pellet target and the results of