545 research outputs found
Stable operation with gain of a double phase Liquid Argon LEM-TPC with a 1 mm thick segmented LEM
In this paper we present results from a test of a small Liquid Argon Large
Electron Multiplier Time Projection Chamber (LAr LEM-TPC). This detector
concept provides a 3D-tracking and calorimetric device capable of charge
amplification, suited for next-generation neutrino detectors and possibly
direct Dark Matter searches. During a test of a 3~lt chamber equipped with a
1010~cm readout, cosmic muon data was recorded during three weeks
of data taking. A maximum gain of 6.5 was achieved and the liquid argon was
kept pure enough to ensure 20~cm drift (O(ppb)~O equivalent).Comment: 7 pages, 6 figures, to appear in Proc. of 1st International Workshop
towards the Giant Liquid Argon Charge Imaging Experiment (GLA2010), Tsukuba
(Japan), March 201
Test of a Liquid Argon TPC in a magnetic field and investigation of high temperature superconductors in liquid argon and nitrogen
Tests with cosmic ray muons of a small liquid argon time projection chamber
(LAr TPC) in a magnetic field of 0.55 T are described. No effect of the
magnetic field on the imaging properties were observed. In view of a future
large, magnetized LAr TPC, we investigated the possibility to operate a high
temperature superconducting (HTS) solenoid directly in the LAr of the detector.
The critical current of HTS cables in an external magnetic field was
measured at liquid nitrogen and liquid argon temperatures and a small prototype
HTS solenoid was built and tested.Comment: 5 pages, 5 figures, to appear in Proc. of 1st International Workshop
towards the Giant Liquid Argon Charge Imaging Experiment (GLA2010), Tsukuba
(Japan), March 201
First operation and drift field performance of a large area double phase LAr Electron Multiplier Time Projection Chamber with an immersed Greinacher high-voltage multiplier
We have operated a liquid-argon large-electron-multiplier time-projection
chamber (LAr LEM-TPC) with a large active area of 76 40 cm and a
drift length of 60 cm. This setup represents the largest chamber ever achieved
with this novel detector concept. The chamber is equipped with an immersed
built-in cryogenic Greinacher multi-stage high-voltage (HV) multiplier, which,
when subjected to an external AC HV of 1 kV, statically
charges up to a voltage a factor of 30 higher inside the LAr vessel,
creating a uniform drift field of 0.5 kV/cm over the full drift length.
This large LAr LEM-TPC was brought into successful operation in the
double-phase (liquid-vapor) operation mode and tested during a period of
1 month, recording impressive three-dimensional images of very
high-quality from cosmic particles traversing or interacting in the sensitive
volume. The double phase readout and HV systems achieved stable operation in
cryogenic conditions demonstrating their good characteristics, which
particularly suit applications for next-generation giant-scale LAr-TPCs.Comment: 26 pages, 19 figure
First operation of a double phase LAr Large Electron Multiplier Time Projection Chamber with a two-dimensional projective readout anode
We have previously reported on the construction and successful operation of
the novel double phase Liquid Argon Large Electron Multiplier Time Projection
Chamber (LAr LEM-TPC). This detector concept provides a 3D-tracking and
calorimetric device capable of adjustable charge amplification, a promising
readout technology for next-generation neutrino detectors and direct Dark
Matter searches. In this paper, we report on the first operation of a LAr
LEM-TPC prototype - with an active area of 1010 cm and 21 cm drift
length - equipped with a single 1 mm thick LEM amplifying stage and a two
dimensional projective readout anode. Cosmic muon events were collected, fully
reconstructed and used to characterize the performance of the chamber. The
obtained signals provide images of very high quality and the energy loss
distributions of minimum ionizing tracks give a direct estimate of the
amplification. We find that a stable gain of 27 can be achieved with this
detector configuration corresponding to a signal-over-noise ratio larger than
200 for minimum ionizing tracks. The decoupling of the amplification stage and
the use of the 2D readout anode offer several advantages which are described in
the text.Comment: 25 pages, 17 figure
A new experiment to search for the invisible decay of the orthopositronium
We propose an experiment to search for invisible decays of orthopositronium
(o-Ps) with a 90% confidence sensitivity in the branching ratio as low as
. Evidence for this decay mode would unambigously signal new physics:
either the existence of extra--dimensions or fractionally charged particles or
new light gauge bosons. The experimental approach and the detector components
of the proposed experiment are described.Comment: Based on a talk given at Workshop on Positronium Physics, Zurich,
Switzerland, 30-31 May 200
First results from a Liquid Argon Time Projection Chamber in a Magnetic Field
A small liquid argon Time Projection Chamber (LAr TPC) was operated for the
first time in a magnetic field of 0.55 Tesla. The imaging properties of the
detector were not affected by the magnetic field. In a test run with cosmic
rays a sample of through going and stopping muons was collected. The chamber
with the readout electronics and the experimental setup are described. A few
selected events were reconstructed and analyzed and the results are presented.
The magnetic bending of the charged particle tracks allows the determination of
the electric charge and the momentum, even for particles not fully contained in
the drift chamber. These features are e.g. required for future neutrino
detectors at a neutrino factory.Comment: 35 pages, 25 figures, version with full resolution figures at
available at http://neutrino.ethz.ch/GLACIER
Feasibility of high-voltage systems for a very long drift in liquid argon TPCs
Designs of high-voltage (HV) systems for creating a drift electric field in
liquid argon TPCs are reviewed. In ongoing experiments systems capable of
approx. 100 kV are realised for a drift field of 0.5-1 kV/cm over a length of
up to 1.5 m. Two of them having different approaches are presented: (1) the
ICARUS-T600 detector having a system consisting of an external power supply, HV
feedthroughs and resistive voltage degraders and (2) the ArDM-1t detector
having a cryogenic Greinacher HV multiplier inside the liquid argon volume. For
a giant scale liquid argon TPC, a system providing 2 MV may be required to
attain a drift length of approx. 20 m. Feasibility of such a system is
evaluated by extrapolating the existing designs.Comment: 8 pages, 13 figures, to appear in Proc. of 1st International Workshop
towards the Giant Liquid Argon Charge Imaging Experiment (GLA2010), Tsukuba
(Japan), March 201
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