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Projects 2011

In 2011, P2IO funded 9 R&D projects:

Ionization detector for CaLIPSO project

D. Yvon (Irfu/DPhP)

The CaLIPSO research programme focused on the realisation of a proof of concept of a highly pixelated liquid ionisation chamber using trimethyl bismuth (TMBi). The aim was to achieve free charge detection by capacitive coupling in an ultra-clean environment (ultra-high vacuum technology) free of electronegative contaminants. In addition, the detection medium is chemically aggressive. If the surfaces used were white (perfectly light-scattering surfaces), this would be a plus. We explored and optimised the resistive ceramic technology and prepared small test devices to demonstrate this technology. We proposed to use the beam equipment available at CSNSM to implant metals on the surface of commercial but pure alumina ceramics.

Description of the work carried out:

  • Resistive ceramics

We decided to deposit a very thin layer of noble metal (Ir) <10 nm on the ceramic surface. The resistivity was measured: a few kOhm.square. A low-intensity, low-energy ion beam was then used to insert this metal into the ceramic surface, and obtain the desired resistivity without too much degradation of the ceramic surface. We finally prepared some samples with a resistivity of a few GOhm.square, after cleaning with deionised water, corresponding to our need.

  • Single pixel prototype

We have designed and developed the technologies necessary to assemble a single-pixel, TMBi-compatible ionisation detector model. Next, we worked on the IDeF-X ASIC, developed for spacecraft experiments. We have shown that, thanks to the flexibility of the ASIC design, this device meets our needs for the reading of CaLIPSO charge signals.

  • Multi-pixel sensor board technologies

We researched subcontractors and ordered a prototype sensor board called "sensor pads 0" according to our set of constraints. We observed that :

  1. The assembly seems to be of good quality and allows the routing of densely pixelated edges (PCB class 6).
  2. The tested boards resisted the strongest chemical attack (hot concentrated sulphuric acid).
  3. The mechanical strength test was not conclusive: the polymer chosen for the assembly (polyimide) proved to be too "soft". The deformations induced by pressure on the detector during pumping on a close volume stressed the thin ceramic layer and caused it to break.
Figure 1 - First prototype of a multilayer detector circuit after the
mechanical strength and vacuum test.

Technological advances on the single-pixel prototype have allowed us to relax the constraints of our specification. We therefore decided to modify the hardware implementation of the routing circuits in the board.

 

Development of a small prototype of Compton telescope with gamma rays

V. Tatischeff (CSNSM) 

Astronomy in the field of gamma rays in the 0.1 - 10 MeV range holds great promise for elucidating many fundamental questions concerning, for example, nucleosynthesis in star explosions (novæ and supernovæ), the origin of cosmic lines and the laws of physics around neutron stars and black holes.

However, once the instruments on board ESA's INTEGRAL observatory are turned off in a few years, this energy field will be inaccessible to astronomers. One of the most promising concepts for the new generation of space-based gamma-ray instruments is the Compton telescope, consisting of two main parts: a trace detector optimized for Compton scattering of cosmic gamma rays and a calorimeter to absorb the scattered photons.

The P2IO project has made it possible to build a small prototype of this kind of instrument using recent advances in detector technology and integrated readout electronics. The prototype combines several thin layers of double-sided tracked silicon detectors (DSSSD) with a cerium-doped lanthanum bromide scintillator (LaBr3:Ce) coupled to a multi-anode photomultiplier tube (MAPMT). The results obtained show that this type of detector is very promising for a future gamma-ray space telescope.

 

 

Astronomy of high angular precision and polarimetry over the threshold of pair creation, MeV-GeV

D. Bernard (IN2P3)

The HARPO project, "Hermetic Argon Polarimeter", demonstrated for the first time the measurement of the polarization of gamma rays with energies in the MeV range. This type of instrument could open two new windows to the Universe.

The first is access to an energy domain for which astronomers are almost blind. The electromagnetic spectrum has been studied in great detail from low-frequency radio waves to high-energy gamma rays (multi-TeV), but if one traces the sensitivity of these observations as a function of photon energy, a large hole appears. This hole, the "MeV gap", is located in the energy range between 0.1 and 100 MeV. If it is possible to access this part of the spectrum, it would be possible to explore the formation of super-massive black holes through the study of blazars, to study gamma bursts, to look for the sign of light dark matter, and to study a number of important astrophysical sources such as pulsars, supernova remnants, and binary systems for which this part of the spectrum is still unexplored.

The two "maps", i.e. the (x,t) and (y,t) projections of the signal collected during the conversion of a 3.93 MeV gamma photon from NewSUBARU's BL01 line, converting it into an e+e-pair in the argon-based gas of the HARPO prototype TPC. The two vertical lines indicate the positions of the cathode (left) and anode (right) of the TPC.

The second window is polarimetry. Measuring the polarization fraction of the radiation emitted by a source allows to understand the physical structure and characteristics of the source, information that is difficult or sometimes impossible to obtain. As many astrophysical objects emit a high power at MeV (gamma-ray bursts, blazars, pulsars...), an instrument with the sensitivity and the ability to perform polarimetry in this energy range would be of great help.

The measurement of the polarization fraction and its angle in the energy range from MeV to GeV, for which photon detection is performed by conversion into an electron-positron pair (e-e+), is now possible thanks to a Time Projection Chamber (TPC), developed by a team at the LLR, to measure the very beginning of the path of the electron and positron in the detector, just after photon conversion, allowing the measurement of the polarization vector of the radiation before multiple scattering dilutes the information.

You can find on this link the publication resulting from this work: https://inspirehep.net/literature/1606056

 

Development and implementation of semi-conductor sensors to probe the Compton recoil electron spectrum and to measure the beam halo after the interaction point of the ATF2 final focus prototype at KEK (Japan)

P. Bambade (LAL)

This project aims at developing appropriate tools and methodology to asses and control beam halo in accelerators for particle physics. This has very high relevance for the operation of high energy high luminosity colliders, since beams must focused down to extremely smell transverse dimensions, with the consequence of driving halo particles out towards the beam pipe at locations close to the interaction point. Beam halo collimation is a particularly tricky and critical aspect of all presently operating and future collider. The knowhow that is developed through this project has thus a high added value in terms of contributing to create acceptable experimental conditions for existing and future colliders for particle physics.

Interaction Point

The primary technical goal of this project was to develop a beam halo profile monitor suitable for operation in the vacuum chamber of the ATF2 beam line at KEK, capable in particular of withstanding a high radiation environment and of achieving very fast measurements over a very large dynamic range. In this context, diamond sensors were chosen. The directly related scientific goal was the investigation and characterization of the beam halo generation mechanisms and transport, both through calculations and measurements at ATF2. A secondary important technologically oriented goal was also learning about diamond sensors more generally, in order to master both the in-house handling of several fabrication aspects, and the usage for a range of diverse conditions. This project funded by P2IO served as an efficient springboard enabling to make a suitable technical proposal and to obtain European funding for it within H2020.

This project has progressed in signifant ways in three of its main areas:

  • Simulation of the beam halo propagation from the entrance of the ATF2 beam line to the planned sensor location after the interaction point.
  • Definition and initial specification of the mono-cristalline CVD diamond sensor geometry, mechanics and readout.
  • Integration at KEK
 

Grid computing with GPUs

D. Chamont (LLR)

Computing industry still continuously improves processors performances, although it is not any more thanks to a frequency rise. The trend is now to increase the number of cores. This is cheaper for what concerns power consumption, yet those new cores are lighter than traditional processors, and individually benefit from a smaller memory. In this future many-core era, the huge legacy code of high energy physics could turn completely unusable, unless we deeply refactor it so to embrace massive parallelism.


This aim of GridCL project is to study the transformation of P2IO software applications in order to exploit efficiently today what looks like most the future many-core hardware: the graphics coprocessors from NVIDIA and/or AMD, and the new “Many Integrated Core” architecture from Intel. The integration of such hardware in computing grids is planned, which are inherently heterogeneous. This is why portable software solutions are favored such as OpenCL, rather than specific dedicated products such as CUDA or TBB.

 

 

SAMpler for PICosecond time pick-off: electronic 1 ps

E. Delagnes (Irfu/DEDIP)

This project aims at the realization of an electronic system for absolute time measurement based on a new chip to be used in AFP in high pile up/high luminosity environment. The SAMPIC chip has been designed by a collaboration including CEA/IRFU/SEDI, Saclay and CNRS/LAL/SERDI, Orsay.

The principle of this chip is as follows: detection of an event of interest, sampling and time estimation, analog-to-digital conversion and readout of the region of interest, all based on a CMOS sensor.

It benefits from both the quick response of a time to digital converter and the versatility of a waveform digitizer to perform accurate timing measurements. Thanks to the sampled signals, smart algorithms making best use of the pulse shape can be used to improve time resolution. A software framework has been developed to analyse the SAMPIC output data and extract timing information by using either a constant fraction discriminator or a fast cross-correlation algorithm. SAMPIC timing capabilities together with the software framework have been tested using pulses generated by a signal generator or by a silicon detector illuminated by a pulsed infrared laser. Under these ideal experimental conditions, the SAMPIC chip has proven to be capable of timing resolutions down to 4 ps with synthesized signals and 40 ps with silicon detector signals.

 

 

A novel antiproton-decelerator concept

D. Lunney (CSNSM)

The question of the real existence of a form of antigravity is a question that physicists have been trying to answer for decades. Faced with the stakes of discovering not only the antigravity effect, but also differences between matter and antimatter that could explain why the latter is almost absent in the observable cosmos, physicists have decided to find out for themselves. Experiments conducted at Cern, such as the one called "GBAR", should verify this. 

The objective of this R&D project is the realization of a new concept of decelerator for the production of antimatter, a subtask of the GBAR (Gravitational Behavior of Antimatter at Rest) experiment at CERN.
The ingredients of antihydrogen are necessarily created at high energy with particle accelerators, whereas efficient synthesis requires slowing them down. Applying atomic physics techniques that have been successfully used to manipulate exotic radioactive species, the project proponents have proposed an electrostatic decelerator facility to provide low-energy antiproton beam pulses of less than 1 keV.

This development relies on very fast switching of a 100 keV drift tube to ground, as well as additional beam optics to prepare the antiproton beam. P2IO funds have been used to build and test such a decelerator. The instrument built is destined for the AD antiproton facility at CERN. Coupled with the ELENA storage ring, the decelerator is to be used to assist in the commissioning of ELENA. Although designed specifically for the GBAR experiment, the new decelerator will benefit all experiments planning to use the ELENA facility.

The schematic design of the antiproton decelerator is shown in the figure below:

The 100 keV antiproton incident beam pulse is decelerated by cylindrical electrodes, held at potentials up to -99 kV. When the pulse enters the drift tube electrode, the voltage is rapidly (100-200 ns) switched from -99 kV to ground. Inside the conductor, the antiprotons feel no potential gradient and remain at an energy of 1 keV at the exit of the drift tube.

During the project, simulations, design, construction and experimental tests were performed. New simulations were necessary halfway through the project, because the specifications of the antiproton beam provided by ELENA became ten times more severe (0.1%). This led to the more optimized two-stage geometry. This work was carried out as part of a master project by T. Ke (M1 - Nuclear Energy, Paristech) from April to August 2014. The first technical drawings have been made for this system and the material has been ordered. All electrodes were machined and mounted in a KF-based vacuum system built from standard size modular components. The decelerator geometry had to be validated before installation in a CF (high vacuum) system, made of non-magnetic 316LN steel.

A test program with proton beam energies up to 10 keV was performed and it was possible to decelerate pulses from 10 keV to 1 keV in 200 ns. These are important results that allow the transition to the 100 keV scale without problems. These results were obtained during the M2 ENSTA-Paristech internship project of A. Pandey (from April to August 2013). The 100 kV isolation transformer was placed under a high voltage platform and the safety elements were assembled. This work, as well as other installation and measurement tasks, were performed during the DUT-measures physiques internship of Y. Zhang, (IUT d'Orsay) from April to June 2014.

Photograph of the deceleration system and high voltage connections

The GBAR experiment addresses questions of fundamental physics, including the symmetry between matter and antimatter, which is at the heart of the two P2IO infinities. GBAR has been approved and a Memorandum of Understanding has been signed by CERN and the 17 collaborating institutes. P2IO played an extremely important and catalytic role for GBAR by providing the equipment needed to build (and test) the prototype decelerator.

In 2014, a new (four-year) ANR grant (called ANTION - coordinated by IRFU-Saclay with CSNSM-Orsay and LKB-Paris as partners) was received. The ANR has provided the equipment and manpower necessary to pursue this work.

Publications resulting from this project:

 

New generation cryogenic sensors for Astrophysics and Cosmology observation

D. Yvon (Irfu/DPhP) 

The goal of the project was the development of an innovative cryogenic sensor with direct applications to Astrophysics and Cosmological observations. Low temperature bolometers arrays have played a key role to this domain (Planck and Herschel space missions, South Pole Telescope observations...) and now pave the way to some major projects concerning CMB B-mode polarization and X-ray space observations. Ferthemore, several projects on particle physics, related to rare event search, are based on similar detectors. The present P2IO project allowed the development of very sensitive high impedance thin films. This solution combines the high sensitivity of a "classical" TES device with the possibility to use high impedance read-out electronics, based on JFET or HEMT transistors. In addition, NbSi TES can be easily adapted to a large variety of experimental requirements.

Design fitted in a 2 inches wafer, composed of 6 different geometries for the NbSi TES. Each "pixel" has four holes that are crossing the substrate. They can be used to fix the sample to a holder with Kevlar wires.

In practice, the energy deposited into the detector induces a temperature increase that is continually monitored by a superconductor thin film. A small temperature variation will give a substantial change in the TES resistance. The major challenge of this project is related to the development of a reliable and reproducible manufacturing process. The process finally approved consists of three consecutive lift-off steps realized by photolithography. The P2IO project has also contributed to the realization of a dedicated low noise amplifier based on HEMT front-end transistors.

This very promising low temperature detector device has potential applications to X-ray imaging. Several P2IO laboratories are supporting the future ATHENA+ space mission, requiring an X-ray calorimetric detector for the 100 eV-15 keV energy range. This NbSi TES cryogenic detector combined with a HEMT based multiplexing scheme is an interesting solution to such type of mission. Beyond the X-ray calorimeters, high impedance TES are also very interesting for low temperature visible light detection and for large mass rare event search bolometers. Neutrino-less double beta decay using low temperature scintillating bolometers and direct dark matter search are typical examples.

 

Superconducting thin film multilayered for SRF accelerating cavity

G. Martinet (IPN)

The main objectives of this project are the development of Nb films with properties corresponding to bulk Nb as well as an evaluation of the potential of SIS nanolayer structures for SRF applications.

Heteroepitaxial and fibrous columnar growth modes have been studied under different conditions in order to determine the optimal deposition conditions for RF surfaces based on Nb films. The influence of incident ion energy and substrate temperature on the structure of the Nb film was investigated. Single crystal Nb films were produced by ECR plasma deposition epitaxy on a variety of crystalline, metallic and insulating substrates.

The growth of Nb ECR films has also been studied on polycrystalline and amorphous substrates. This study reveals that by varying the substrate temperature and incident Nb ion energy, the film structure varies. The ECR films reveal concentrations of light impurities such as hydrogen that are several orders of magnitude lower than for bulk Nb surfaces prepared in the state of the art. It has been shown that RRR values for Nb films can be varied from single digit values to unprecedented values comparable to bulk Nb. Superconducting gap measurements also reveal values equivalent to the superconducting gap of bulk Nb. 

The development of SIS multilayer film structures following the concept proposed by Gurevich has been studied with NbTiN and AlN for high Tc and dielectric films respectively. Good quality NbTiN monolayers were produced by DC magnetron sputtering at different thicknesses. Tc equivalent to bulk NbTiN is obtained for films with thickness > 1 um. The first NbTiN films produced by HiPIMS were produced with a Tc of the order of 16.6 K. SQUID magnetometry measurements for very thin NbTiN/MgO films reveal a modest increase in the critical field Hc1. Good quality NbTiN/AlN multilayer structures have been produced.

RF characterization of these SIS structures deposited on bulk Nb and on Nb/Cu films reveal that this concept has the potential to delay fluxon penetration and improve RF performance for SRF cavities beyond bulk Nb. 

 
#112 - Last update : 10/11 2021

 

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