During the second half of 2008, SDI has supported the design and manufacturing of the calibration bench of the electromagnetic calorimeter supermodules of ALICE. This calibration bench is composed of 16 large scintillators (1.5 m), located above and below the detector, allowing signal and locate the cosmic muons passing through the detector.
In total, 14 supermodules were calibrated within the ARIANE hall at LPSC using this equipment with a dispersion of 2 to 3%, much lower than specified in the original specifications.
Contact : Muraz Jean-François
AUGER NORTH site Project
For the North site project of Pierre Auger Observatory (Colorado, USA), the SDI studied a new photo-detection device for tanks.
Indeed, the detectors of Auger surface shall be brought to operate continuously. The tanks are arranged outdoors, the photomultiplier (PM) and associated electronics are subject to significant climatic variations (0 to 50 ° C, humidity).
This would allow all be in the form of a compact sensor unit facilitating repairs and control.
Two systems are studied, based on a plastic conical body molded by shape close to that used at present on the South site to isolate the PM from the light. The first one contains a window of entry to Plexiglas that fits the photocathode surface.
The second leaves free this surface, but contains a double torique joint at the level of the collar of the PM. In both proposed solutions, the systems are closed by a metallic bottom to which will be fixed the electronics.
The objective was to integrate 700 photomultipliers ( PM) which represents the whole detection of the detector matrix Cerenkof ( Rich) of AMS. A collaboration between the electronic department and the SDI allowed to bring to a successfull conclusion this long and complex activity, which required the establishment of a procedure which can be summarized in the following way:
- Equipment of all the PMs with their electronics then sorting by gain.
- Glueing of an optical gum on the window of the PM (used product: gel Dow Corning 93-500, " potting "). The precise dosage of the quantity of potting is made by a machine of removal.
- Drying during 12 hours in 40°C
- Integration of the group PM+gum in a plastic hull serving as mechanical support and as mold for the potting. To avoid the potting leaks during the following operation, a gel Dow Corning run is applied between the optical gum and the bottom of the hull, (polymerization 8 hours).
- Precise dosage of the potting in 10 %, then a long and meticulous degassing of the mixture is obtained for the complete evacuation of the air imprisoned into the mixture.
- The mixture is put in syringe and injected in the free space between hulll and PM, by an opening planned for that purpose. Approximately 7 grams of mixture are used by PM.
- Polymerization 12 hours at ambient temperature ends the operation.
The role of the Potting operation is the mechanical preservation of the PM in its hull and the isolation of the electronics from initiatings at high voltage. Then comes the operation of Cotting, intended to protect and in isolated all the visible part of the electronics, (flex connector, asic, etc..). The product used and Nusil CV 1152 of Silicone Technology, applied to the brush and which requires 12 hours of polymerization.
The PM so prepared were sent in the CIEMAT in Madrid in the year 2005.
The team then made on-the-spot for the guides of lights on the optical gum glueing operation for every PM. Guide were sorted out at first then verified in binocular microscope so as to prevent any mechanical defect, stripes, pixel except plan, opacity. Then, the following operations are made:
For this experiment, the department participated in the integration of the optical modules of the detector as well as in the activities of tests and checks of the matrix consisted of 1600 photomultipliers (PM).
This integration consisted in the assembly of the focal plan which consists of 25 modules containing each 4 sub-modules. Every sub-module is equipped with 16 photomultipliers. The PM was beforehand coupled according to their sizes and to their gain and their implementation (equipment) was made according to this information.
A seal between the printed circuit and the PM base was set up, so as to be able to make a "potting", that is an insulation of the PM electrodes carried at high voltage. This allows to eliminate the low-pressure strains owed to the " minimum of Paschen " (the more the pressure of the air decreases and the more the electric shock arises at low voltage.
The curve of Paschen, which represents the tension of strain according to the distance inter electrodes and of the pressure, reaches a minimal value called the " minimum of Paschen "). The "potting" was made by injecting a resin of type Mapsil 213 B, 13 grams of product were used by sub-module and 18 minutes on average are necessary for every injection, the polymerization being made at ambient temperature.
An operation of "coating" was then made for the same reasons as previously (Paschen). This one consists in soaking every sub-module, at the level of the printed circuit and on every component, with a resin (Nusil CV1152), applied to the brush, which insures a protection of surface. This activity required the putting in steam room of sub-modules for 6 hours in 40 ° C.
Finally, the third operation was also realized to avoid the strains. This one corresponds to the addition of a layer of micro balloons (micro glass balls) mixed in the resin (Mapsil 213 B), and applied by syringe on the reverse of sub-module. Tests of every sub-module at high-voltage and vacuum were then led to verify that there were no strains in the passage of the « minimum de Paschen ».
The integration continues then by the assembly of sub-modules on the railing support, the check of the focal plan, the mechanical tightening and the implementation of optical fibers of test. The assembly of the electronic boards of "Front-end" acquisition is then made with the implementation of the thermal bridges on the railing support to evacuate the heat via the small columns of assembly of modules.
To finish, having equipped the focal plan of probes of temperature, circuits of connection of type " Flex " and supplies, the plan of tiles of aérogel is installed. It is constituted of two sheets of Mylar tense and stuck on an aluminum frame containing the tiles of aérogel. Two mechanical protections of nest of bee type are then installed on the front and on the back of the device.
All these operations required not far from 12 working months, from January, 2006 till January, 2007.
Within the framework of the educational activity towards high schools (ECRINS), the SDI developed two compact detection of cosmic rays devices baptized " Mini ECRINS ". These systems are constituted each of both plastic scintillateurs, associated to two photomultipliers supplied by batteries. The acquisition of the signals is permformed by a mini oscilloscope USB (PicoScope®) piloted by a LabVIEW© dedicated program . If we use a laptop computer, these devices become completely autonomous and transportable in an appropriate suitcase.
These devices are realizations of the SDI, not only due to their design and their manufacturing, but also due to their use within the framework of educational activities in 2007 as the physics exposition at St Ambroise High School of Chambéry and Physics Olympiads at Pierre and Marie Curie High School of Grenoble in 2007.
Started at the beginning of 2003, our participation in the n-DVCS experiment, (Deeply Virtual Compton Scattering one the neutron) at the hall A of Jefferson Laboratory (JLab, Virginia, USA) consisted of the design and the realization of a labeling of charged particles (Tagger) detector. Tagger consists of 2 superimposed layers of plastics scintillators (57 elements of 11 different forms), forming three quarters of a circle and fit the spherical shape of the reaction chamber of the DVCS experiment. The wanted main objective was to obtain a very good uniformity of the scintillators response following the zone of the scintillator crossed. To reach it, we brought to a successful conclusion the R&D phasis, realized several prototypes allowing to determine and to optimize the scintillators shape, the geometry of the guides of light as well as typifies it of photomultipliers (PM). These studies allowed to select the scintillator EJ 200 (ELJEN) 2 cms in thickness whose manufactured faces are raw of diamond sawing. Every scintillator is associated with a guide of light in PMMA stuck with some UV glue DYMAX 3-20262-T. Slats so constituted are wrapped in the aluminum foil of 30 µm with thickness then in the sheet of TEDLAR® black and totally opaque. Photomultipliers are Hamamatsu R7877 in 8 floors of amplification chosen because of the low congestion and of the difficult experimental conditions: in sight direct of the target, at a distance of 1 m in an electromagnetic environment. The interface between the PM and the guide is constituted by optical gel BICRON BC630.
Year 2004 will have been a key year for the experiment with the manufacturing, the assembly and the on-site assembly of the experiment. The assembly within the LPSC started at the beginning of 2004 to end in June, 2004. The assembly to JLab took place from June 28th till July 8th, 2004.
We took in charge:
The grips of data took place during all autumn, 2004.
Contact : Muraz Jean-François
The experimental device PEPPo establishes a new line of beam located in the injector of Jefferson Laboratory (JLab, Virginia, the USA).
This detector contains a first target of tungsten in which positrons are converted in polarized photons; the measure of the absorption of these photons in a target polarized by 7,5 cms of iron according to the orientation of the initial polarization of positrons (that is the primary beam of electrons) or of the polarization of the target allows to determine the positrons polarization.The transmitted photons are measured in an electromagnetic calorimeter constituted of 9 crystals of Iodide of Cesium doped in Thallium and read by type R6236-01's photomultipliers (Hamamatsu).
The polarimeter with transmission of PEPPo arises from the polarimeter of the experiment E166 at SLAC which operated in the same range of energy. The SDI took in charge all the necessary modifications to adapt the polarimeter to the specific needs for the PEPPo experiment.This device contains an electromagnetic calorimeter, a magnet of analysis as well as an armor plating of consequent lead (3t) surrounding the calorimeter. These 3 elements are placed on a table the mobile upper tray of which allows to adjust exactly the position.
The polarimeter was completely designed, realized then installed on the line of beam of JLab by the technical teams of the LPSC. The Detectors and Instrumentation Department assured the technical coordination of the project, the design of the polarimeter, the realization of a cosmic trigger, the design and the realization of a system LED of calibration, the implementation and the participation the tests of the calorimeter, the management and the follow-up of the shipping of the whole polarimeter and its assembly to JLab.
This document redraws, in image, the various stages made for the realization af the polarimeter.
Contact : Muraz Jean-François
- Photo-detectors characterization and tests.
- Design, elaboration and on-siteimplementation for the whole atmospheric sparks detection.
- Implementtation of 3G telemetry and temporary acquisition system.
Stassi Patrick: Photodetection - Telemetry
Marton Marc : Detector Design/CAD
Chala Mohammed : Detector Assembly
Bernard Christophe : Detector Assembly
- R&D on the supply of Quartz pure ultras.
- R&D reading of the Cherenkov light by means of SiPM
Contact : Muraz Jean-François