The autoradiography is an imaging technique able to locate in 2 dimensions molecules labeled with beta radioactive emitters. The usual technique in use is based on solid device, mostly films or ...phosphor screens. We report on tests performed with PIM (parallel ionization multiplier) on microscope slides demonstrating that MPGD (micro pattern gas detector) incorporating micromegas micro-meshes have to be considered for a next generation of beta-imager. The main advantages come from the high spatial resolution measured (25 mum FWHM in two dimensions) and from the event by event reconstruction position measurement resulting in ldquoon-linerdquo imaging availability in which no ldquoafter developmentrdquo have to be performed.
A low-resistivity RPC for the ALICE dimuon arm Arnaldi, R; Baldit, A; Barret, V ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
09/2000, Volume:
451, Issue:
2
Journal Article
Peer reviewed
In view of ALICE, the dedicated Heavy-Ion Experiment at LHC, a Resistive Plate Chamber (RPC) with electrodes made of low-resistivity bakelite (
ρ≃3.5×10
9
Ω
cm
) has been tested at the CERN SPS both ...in streamer and in avalanche mode. The chamber has shown a stable behaviour and excellent rate capability: its efficiency is better than 95% for local particle fluxes of about 1 and 10 kHz/cm
2 for operation in streamer and in avalanche mode, respectively. The cluster size and the time resolution have also been measured for both modes of operation.
β -Imaging with the PIM device Samarati, J.; Charpak, G.; Coulon, P. ...
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment,
12/2004, Volume:
535, Issue:
1
Journal Article, Conference Proceeding
Peer reviewed
The
β
autoradiography is an imaging technique which allows the two dimensional localisation of the distribution of a molecule labelled with
3
H or
14
C in tissue sample. In collaboration with the ...Biospace Mesures company, we developed a new micropattern gaseous detector called Parallel Ionization Multiplier (PIM) dedicated to the
β
imaging. The images obtained show characteristics in adequation with the autoradiography requirements as a 2D spatial resolution (FWHM) of
50
μ
m
(respectively
60
μ
m
) and an efficiency of 85% (respectively 50%) for
3
H (respectively
14
C).
New amplifying structures can be built exploiting the electric properties of metallic meshes a few microns thick. They can be used for preamplification with a variety of gaseous detector or for ...one-stage amplification. Detection efficiency better than 80% and 50μm (FWHM) 2D accuracy on A4 sensitive areas, with uncollimated sources of 3H or 14C, is achieved with such preamplifiers.
With two amplifying stages, the discharge rate with α sources is reduced by a factor close to 1000 compared to single-stage amplification at equivalent gain values. These results have been obtained on a new structure that has been developed, called PIM for parallel ionization multiplier. PIM is made of a thin sandwich of two metallic meshes separated by a new insulating spacer whose geometrical characteristics are made possible by state-of-the-art developments in laser etching technologies. A drastic improvement has been found in the minimal distance between spacers necessary to keep the distance between the metallic meshes stable.
An attractive method of two-dimensional localization based on charge division with Ni–Cr resistive strips has been adapted to a Micromegas detector taking advantage of its high gain. Along the ...strips, depending on the signal to noise ratio,
1.05
mm
–
300
μm
spatial resolutions (respectively, 0.80–0.23% of the strip length) are obtained with an
3
H
source. For trajectory reconstruction in magnetic fields, these accuracies could match most of the localization constraints requested for measurements of the non-bending coordinate. In the direction perpendicular to the strips, localizations better than
100
μm
could be achieved using the center of gravity of the charges.
A new amplifying structure has been developed for beta imaging detectors: the Parallel Ionization Multiplier (PIM). PIM is made of a thin sandwich of two metallic micromeshes separated by a new laser ...machined insulating spacer. This structure allows high gain (10
5) with a good efficiency and a two-dimensional spatial resolution below 50
μm without strong discharge limitation. The capabilities of the PIM are now investigated in order to be used by high-energy physics experiments. A prototype of a tracking detector for charged particles using the PIM structure will be described. Thanks to the very small avalanche extension, the use of a highly segmented anode is possible. This detector would support high rate running conditions of hadron experiment.
We report on discharge rate measurements performed with Parallel Ionization Multiplier (PIM) detectors in a 10
GeV hadron beam. Various PIM configurations with two amplification gaps are considered, ...and compared to a Micromegas-like single-gap configuration. When the two stages of amplification are placed directly on top of one another, the discharge rate is found to be systematically greater than in the single-gap case, whatever the electric fields are in the two stages. Moreover, the rate is strongly correlated with the total thickness of the amplification gap. However, when the two amplification stages are separated by a transfer gap, the discharge rate can be reduced by up to a factor of 50 at a gain of 5000 with a
Ne
+
10
%
CO
2
gas mixture.
Influence of temperature and humidity on bakelite resistivity Arnaldi, R; Baldit, A; Barret, V ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2000, Volume:
456, Issue:
1
Journal Article
Peer reviewed
Open access
The use of phenolic or melaminic bakelite as RPC electrodes is widespread. The electrode resistivity is an important parameter for the RPC performance. As recent studies pointed out, the bakelite ...resistivity changes with temperature and is influenced by humidity. In order to gain a quantitative understanding on the influence of temperature and humidity on RPC electrodes, we assembled an apparatus to measure resistivity in well-controlled conditions. A detailed description of the experimental set-up as well as the first resistivity measurements for various laminates in different environmental conditions are presented.
Study of the resistive plate chambers for the ALICE Dimuon Arm Arnaldi, R; Baldit, A; Barret, V ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2000, Volume:
456, Issue:
1
Journal Article
Peer reviewed
Open access
The trigger system for the ALICE Dimuon Arm will be based on Resistive Plate Chambers (RPC). A RPC prototype, with electrodes made of low-resistivity bakelite (
ρ∼3×10
9
Ω
cm
) has been tested both ...at the SPS and at the Gamma Irradiation Facility. The results for the operation in the streamer mode are presented here.
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