H. Mathez

Construction and commissioning of a technological prototype of a high-granularity semi-digital hadronic calorimeter

A large prototype of 1.3m3 was designed and built as a demonstrator of the semi-digital hadronic calorimeter (SDHCAL) concept proposed for the future ILC experiments. The prototype is a sampling hadronic calorimeter of 48 units. Each unit is built of an active layer made of 1m2 Glass Resistive Plate Chamber(GRPC) detector placed inside a cassette whose walls are made of stainless steel. The cassette contains also the electronics used to read out the GRPC detector. The lateral granularity of the active layer is provided by the electronics pick-up pads of 1cm2 each. The cassettes are inserted into a self-supporting mechanical structure built also of stainless steel plates which, with the cassettes walls, play the role of the absorber. The prototype was designed to be very compact and important efforts were made to minimize the number of services cables to optimize the efficiency of the Particle Flow Algorithm techniques to be used in the future ILC experiments. The different components of the SDHCAL prototype were studied individually and strict criteria were applied for the final selection of these components. Basic calibration procedures were performed after the prototype assembling. The prototype is the first of a series of new-generation detectors equipped with a power-pulsing mode intended to reduce the power consumption of this highly granular detector. A dedicated acquisition system was developed to deal with the output of more than 440000 electronics channels in both trigger and triggerless modes. After its completion in 2011, the prototype was commissioned using cosmic rays and particles beams at CERN.

HARDROC1, readout chip of the Digital HAdronic CALorimeter of ILC

HARDROC (HAdronic Rpc Detector ReadOut Chip) is the very front end chip designed for the readout of the RPC or Micromegas foreseen for the Digital HAdronic CALorimeter (DHCAL) of the future International Linear Collider. The very fine granularity of the ILC hadronic calorimeters (1cm2 pads) implies a huge number of electronics channels (4 105 /m3) which is a new feature of “imaging” calorimetry. Moreover, for compactness, the chips must be embedded inside the detector making crucial the reduction of the power consumption to 10 µWatt per channel. This is achieved using power pulsing, made possible by the ILC bunch pattern (1 ms of acquisition data for 199 ms of dead time). HARDROC readout is a semi-digital readout with two or three thresholds (2 or 3 bits readout respectively in hardroc1 and hardroc2) which allows both good tracking and coarse energy measurement, and also integrates on chip data storage. The 64 channels of the 2nd prototype, HARDROC2, are made of: • Fast low impedance preamplifier with a variable gain over 8 bits per channel • A variable slow shaper (50-150ns) and Track and Hold to provide a multiplexed analog charge output up to 15pC. • 3 variable gain fast shapers followed by 3 low offset discriminators to autotrig down to 10 fC up to 10pC. The thresholds are loaded by 3 internal 10 bit- DACs and the 3 discri outputs are sent to a 3 inputs to 2 outputs encoder • A 128 deep digital memory to store the 2*64 encoded outputs of the 3 discriminators and bunch crossing identification coded over 24 bits counter. • Power pulsing and integration of a POD (Power On Digital) module for the 5MHz and 40 Mhz clocks management during the readout, to reach 10µW/channel The overall performance of HARDROC will be described with detailed measurements of all the characteristics. Hundreds of chips have indeed been produced and tested before being mounted on printed boards developed for the readout of large scale (1m2) RPC and Micromegas prototypes. These prototypes have been tested with cosmics and also in testbeam at CERN in 2008 and 2009 to evaluate the performance of different kinds of GRPCs and to validate the semi-digital electronics readout system in beam conditions.

A cost-effective monitoring technique in particle therapy via uncollimated prompt gamma peak integration

For the purpose of detecting deviations from the prescribed treatment during particle therapy, the integrals of uncollimated prompt gamma-ray timing distributions are investigated. The intention is to provide information, with a simple and cost-effective setup, independent from monitoring devices of the beamline. Measurements have been performed with 65 MeV protons at a clinical cyclotron. Prompt gamma-rays emitted from the target are identified by means of time-of-flight. The proton range inside the PMMA target has been varied via a modulator wheel. The measured variation of the prompt gamma peak integrals as a function of the modulator position is consistent with simulations. With detectors covering a solid angle of 25 msr (corresponding to a diameter of 3–4 in. at a distance of 50 cm from the beam axis) and 108 incident protons, deviations of a few per cent in the prompt gamma-ray count rate can be detected. For the present configuration, this change in the count rate corresponds to a 3 mm change in the proton range in a PMMA target. Furthermore, simulation studies show that a combination of the signals from multiple detectors may be used to detect a misplacement of the target. A different combination of these signals results in a precise number of the detected prompt gamma rays, which is independent on the actual target position.

A low noise and high dynamic charge sensitive amplifier-shaper associated with Silicon Strip Detector for compton camera in hadrontherapy

An 8-channel Front End Electronics (FEE) circuit has been designed and fabricated in 0.35 11m CMOS process from Austria Micro System to be coupled with the Silicon Strip Detector (SSD) of the Compton Camera for quality control of hadrontherapy. Each channel includes a Charge Sensitive Amplifier (CSA) followed by two parallel CR-RC shapers. Slow and fast shapers, with 1 IlS and 15 ns shaping time, are used to measure the energy and to time stamp all events respectively. The two sides of the SSD are read thanks to a configurable system for holes and electrons. The CSA presents an open loop gain of 67 dB and 90 degrees phase margin assuring a high stability. The circuit has been successfully tested. The test results are in good agreement with analytic and simulation calculations. Here, we describe the principles and present measured performances of the prototype. A high linearity over the range of 3E3 to 3E6 electrons is reached with a conversion gain of 3.6 mV/fC. The circuit achieves an ENC (Equivalent Noise Charge) of 412 electrons rms. 75% of the total noise is generated by the small value of the feedback resistor chosen to avoid pile up phenomenon due to the lE5 hits/s occupancy rate. A cross-talk of 2 % was measured, 99% of which is due to the power supply disturbances. The power supply dissipation is 21 mW/channel for 3.3 V supply voltage. The area of this design is 2871x1881 μm2 including pads.

Very fast front end ASIC associated with multi-anode PMTs for a scintillating-fibre beam hodoscope

For developing a scintillating-fibre beam monitor, we have designed a front-end 16-Channel readout chip (version 2) to be associated with Multi-anode photomultipliers Ma-PMTs (Hamamatsu H8500) in a 0.35 μm BiCMOS process. Each channel of the ASIC consists of one input current conveyor driving separately a current comparator for signal event detection and a charge-sensitive amplifier (CSA) for signal charge measurement. The ASIC has brought significant improvements compared to its previous version: larger input dynamic range (53 dB against 33 dB), lower power consumption (11 mW/channel instead of 22 mW/channel under a 3.3-V supply), lower noise (4 fC versus 19 fC in Equivalent input Noise Charge, or ENC) and a better phase margin for optimizing stability and speed. This dedicated chip had been used in a beam test at HIT (Heidelberg Ion-Beam Therapy Center). System testing has shown achievements of 1 mm spatial resolution (size of the scintillating fibers) and a 4 MHz count rate. The main limitation comes from the Ma-PMTs which saturates at such a frequency. The ASIC operates normally with satisfied performances.

111: Real-time monitoring of the ion range during hadrontherapy: An update on the beam tagging hodoscope

An update on the beam tagging hodoscope J. Krimmer, L. Caponetto, X. Chen, M. Chevallier, D. Dauvergne, M. De Rydt, S. M. Deng, J.-L. Ley, H. Mathez, C. Ray, V. Reithinger, E. Testa,Y. Zoccarato Université de Lyon, Université Claude Bernard Lyon 1, CNRS/IN2P3, Institut de Physique Nucléaire de Lyon, 69622 Villeurbanne, France, Instituut voor Kernen Stralingsfysica, K.U.Leuven, Celestijnenlaan 200D, B-3001 Leuven

Charge Sensitive Amplifier (CSA) in cold gas of Liquid Argon (LAr) Time Projection Chamber (TPC)

This paper presents our work on a 8-channel low noise Front-End electronic coupled to a Liquid Argon (LAr) TPC (Time Projection Chamber). Each channel consists of a Charge Sensitive Amplifier (CSA), a band pass filter and a 50 Ohms buffer as line driver. A serial link based on a ‘i2c-like’ protocol, provides multiple configuration features to the circuit by accessing slow control registers. Only the CSA part is described in this paper. The feedback network of the CSA is made of a capacitance and a resistor. Their values are respectively 250 fF and 4 ΜΩ. An input referred noise of, at most, 1500 e-rms must be achieved at −100°C with an input detector capacitance of 250 pF to ensure a correct measurement of the minimal signal of 18000e-(2.88 fC). The power consumption in this cryogenic setup must be less than 40 mW from a 3.3 V power supply.

16-channel readout ASIC for a hodoscope

This paper presents a front-end 16-channel readout chip to be coupled with PMs (photomultipliers) or APDs (avalanche photodiodes), which is designed in a BiCMOS process for a fast beam tagging system used in ion-therapy. Each channel consists of a current conveyor and two separate output stages: one is a current comparator for signal event detection, and the other is a charge sensitive amplifier (CSA) for signal charge measurement. The current conveyor employs super-common-base (SCB) transistor structure, which allows the input impedance to be as low as a few ohms. The current-mode architecture with current comparator also makes it possible to improve performances especially in speed and dynamic range.

Scintillation Signal in XEMIS2, a Liquid Xenon Compton Camera with 3γ Imaging Technique

The XEMIS project (XEnon Medical Imaging System), which makes use of 3γ imaging technique and liquid xenon Compton camera, aims to make a precise 3D localization of a specific radioactive emitter and to reduce drastically (100 times less) the injected activity to the patient in cancer diagnosis. The 3γ imaging is characterized by the simultaneous detection of 3 γ-rays emitted by 44Sc which is a (β+, γ) emitter. The second prototype XEMIS2 is a liquid xenon cylindrical camera for small animal imaging. The active volume of XEMIS2 is surrounded by a set of VUV-sensitive Hamamatsu photomultipliers, for the scintillation signals detection. A pulse-shaping amplifier was tested in XEMIS1 for the readout of the scintillation signal of the PMT. The typical output pulse shows a relatively good performance of the pulse-shaping amplifier providing a possible solution for XEMIS2 scintillation DAQ. Meanwhile, the pulse-shaping amplifier and the constant fraction discriminator (CFD) have lay the foundation of the preliminary design of XEMIS2 scintillation signal detection chain.

XEMIS: Liquid Xenon Compton Camera for 3γ Imaging

An innovative liquid xenon Compton camera project, XEMIS (XEnon Medical Imaging System) has been proposed by SUBATECH laboratory, for a new functional medical 3γ imaging technique based on the detection in coincidence of 3 γ-rays. The purpose of this 3γ imaging modality is to obtain a 3D image using 100 times less activity than in current PET systems. The combination of a liquid xenon time projection chamber (LXe TPC) and a specific (β+, γ) radionuclide emitter 44Sc is investigated in this concept. In order to provide an experimental demonstration for the use of a LXe Compton camera for 3γ imaging, a succession of R&D programs, XEMIS1 and XEMIS2, have been carried out using innovative technologies. The first prototype XEMIS1 has been successfully validated showing very promising results for energy, spatial and angular resolutions with an ultra-low noise front-end electronics. The second phase dedicated to a 3D imaging of small animals, XEMIS2, is now under installation and qualification, while the characterizations of ionization signal using Monte Carlo simulation has shown preliminary good performances for energy measurement.