UCN - Capacitive level probes
As part of a collaboration between the LPSC UCN group and the Paul Scherrer Institute, the SDI developped its experience in the cryogenics field to take in hand the thorny problem of the cryogenic liquid deuterium level probe design and realization, mechanically resisting at the product solidification.
The proposed solution is a capacitive probe constituted of two concentric tubes adjusted in a extremely precise way. This very reliable solution does not exist in the market.
These probes are electrically bound with a small electronic oscillator, which signal output presents a frequency proportional to the level of liquid.
Tests in ice showed that solidification of the liquid containing the probe does not damage it and does not modify its characteristics.
Four probes were so realized 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 main goal was to obtain 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 in terms of manufacturing, assembly and on-site assembly of the experiment. The assembly within the LPSC started at the beginning of 2004 to end in June, 2004. The assembly at JLab took place from June 28th till July 8th 2004.
We took in charge :
Data acquisition took place in autumn 2004.
This document redraws with images the various steps accomplished to build the tagging detector.
Contact : Jean-François Muraz
The objective was to integrate 700 photomultipliers ( PM) which represents the whole detection of the detector matrix Cherenkof ( 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:
Contact : Marc Marton
Martin Puplett Interferometer
For the CMB Survey (Cosmic Microwave Backgroung), the experiments have for objective the measurement of the polarization of the radiation.
On the other hand, the LPSC, in association with the Ultra low Température group at Louis Neel Institute (ex CRTBT), was responsible for the manufacturing project of the mechanical part of an Martin Puplett interferometer (MPI, photo), this device was dedicated to the tests of arrays in the millimetric and submillimétric length domain.
In 2004, the department participated actively in the sizing of the interferometer and in the specification of components. The department of study and mechanical realization of the LPSC then designed and realized all the parts of the Martin Puplett during year 2005. The final assembly and the installation at CRTBT took place in December, 2005 (collaboration of the SDI and the engineering workshop).
Contact : Myriam Migliore
Planck satellite - Control systems
During year 2002, the prototype of the control system of the 20K cryo-generator of the Planck satellite , developped by the Jet Propulsion Laboratory (JPL), laboratory of the NASA of Pasadena, USA, was made.
Two campaigns of tests in 2002 and one in 2003 were necessary to qualify material and software aspects of this device. These tests took place in close collaborations with the electronics department of the LPSC. The prototype being directly connected to the cryo-generator prototype itself, on the JPL site. The SDI, which is responsible for a part of the technical project management, organized these tests as well as the associated procedures. we also assured the development and the implementation of of the command system and an interactive application under LabVIEW, allowing to pilot the whole device by simulating the interfaces of the satellite.
These campaigns of check were a big success, demonstrating the sensible character of the solutions of design proposed by the laboratory as well as the smooth running of the communication between the teams of the LPSC and the JPL.
After a long period of definition of the characteristics and the interfaces, the prototype command system of the cryo-generator 100mK of the satellite could be made has the end of year 2003.
The tests of qualification of this system took place in the year 2004, on the site of Air Liquide of Sassenage, manufacturer of the cryo-generator. The SDI developed the control system and an application under LabVIEW, capable of simulate the definitive piloting of the device (Data Processor Unit, DPU) developed by the LAL at Orsay.
In 2003, within the ULTRA experiment framework, the SDI widely contributed to the manufacturing, the implementation and the on-site installation of the ET-Scope set, intended to detect the particles from atmospheric sparks in association with the INFN of Turin and the IASF teams of Palermo, Italy.
These detectors among five, constituted of wide plates of scintillateurs associated to photomultipliers, were deployed near the Mount Cenis dam in Savoy twice during two measuring campaigns of two weeks, in October, 2002 and June, 2003.
During these campaigns, the department assured the implementation of the on-site device as well as the logistics and the provision of an acquisition system. The data measurements in which we widely participated, were made during moonless nights, necessary conditions for good measurements.
Furthermore, a new type of detector (Belenos), developed by the SDI, intended to measure the Ultraviolet signals (250-450nm) associated to the atmospheric sparks also installed. The preliminary tests made in July, 2003 on the first prototype demonstrated the efficiency of this device.
At the end of the year on 2003 the ET-Scope was installed on site of the LPSC to make tests and long term measurements.
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