Particle Physics Detectors Research Articles

Radiation Hard Silicon Strips Detectors for the SLHC

While the Large Hadron Collider (LHC) began taking data in 2009, scenarios for a machine upgrade to achieve a much higher luminosity are being developed. In the current planning, it is foreseen to increase the luminosity of the LHC at CERN around 2018. As radiation damage scales with integrated luminosity, the particle physics experiments will need to be equipped with a new generation of radiation hard detectors. This article reports on the status of the R&D projects on radiation hard silicon strips detectors for particle physics, linked to the Large Hadron Collider Upgrade, super-LHC (sLHC) of the ATLAS microstrip detector. The primary focus of this report is on measuring the radiation hardness of the silicon materials and the detectors under study. This involves designing silicon detectors, irradiating them to the sLHC radiation levels and studying their performance as particle detectors. The most promising silicon detector for the different radiation levels in the different regions of the ATLAS microstrip detector will be presented. Important challenges related to engineering layout, powering, cooling and reading out a very large strip detector are presented. Ideas on possible schemes for the layout and support mechanics will be shown.

Radiation tolerance of a column parallel CMOS sensor with high resistivity epitaxial layer

CMOS Monolithic Active Pixel Sensors (MAPS) demonstrate excellent performances in the field of charged particle tracking. A single point resolution of 1–2 μm and a detection efficiency close to 100% were routinely observed with various MAPS designs featuring up to 106 pixels on active areas as large as 4 cm2[1]. Those features make MAPS an interesting technology for vertex detectors in particle and heavy ion physics. In order to adapt the sensors to the high particle fluxes expected in this application, we designed a sensor with fast column parallel readout and partially depleted active volume. The latter feature was expected to increase the tolerance of the sensors to non-ionizing radiation by one order of magnitude with respect to the standard technology. This paper discusses the novel sensor and presents the results on its radiation tolerance.

Measurement of the thermal resistance of VCSEL devices

In the context of particle physics detector development, the environmental conditions will change with the increasing capabilities of the accelerators to deliver more particles at higher energies. Since currently the increase of energy above the 14 TeV the LHC is designed for will not be the priority, the increase of luminosity will dominantly change the conditions in which particle detectors will be operated. A higher number and therefore flux of particles per collision through the detectors leads to higher radiation dosages the components must withstand. To operate and read out even the innermost detectors under these conditions electronics and optical components must be developed accordingly. For semiconductor lasers, on which we will concentrate here, it has been found, that an inner temperature increase has direct impact on the light power emitted by the device.It has been found that the effects of radiation on the behavior of semiconductor lasers are convolved with those of temperature. An optimized coupling to the cooling of the laser device reduces the thermal effects in the material. Therefore, a test stand to qualify the effect of heat in the device and the adoption of the heat sink has been realized. In this paper we present first measurements to prove the functionality of the setup.

Free-space optical interconnects for cable-less readout in particle physics detectors

Particle physics detectors utilize readout data links requiring a complicated network of copper wires or optical fibers. Upgrades to such detectors may require additional bandwidth to be provisioned with limited space available to route new cables or fibers. In contrast, free-space optical interconnects will offer cable-less readout, thereby resulting in significant reductions of material and labor to install and manage the cables. A collaborative effort between Fermilab and Vega Wave Systems is pursuing the development of a unique free-space optical link design that utilizes the transparency of silicon at wavelengths including 1310 nm and multiple wavelengths used in standard telecommunications applications such as coarse wavelength division multiplexing (CWDM). The first step in the pursuit of that design is a proof that the concept may be viable. To that end, experiments have been performed to characterize the bit error rate performance of a prototype link over a free-space optical path and through doped silicon at multi-gigabit rates. These experiments have demonstrated that operation within acceptable bit error rates is possible using single and multiple wavelength transmission arrangements.

Liquid xenon detectors for particle physics and astrophysics

This article reviews the progress made over the last 20 years in the development and applications of liquid xenon detectors in particle physics, astrophysics and medical imaging experiments. We begin with a summary of the fundamental properties of liquid xenon as radiation detection medium, in light of the most current theoretical and experimental information. After a brief introduction of the different type of liquid xenon detectors, we continue with a review of past, current and future experiments using liquid xenon to search for rare processes and to image radiation in space and in medicine. We will introduce each application with a brief survey of the underlying scientific motivation and experimental requirements, before reviewing the basic characteristics and expected performance of each experiment. Within this decade it appears likely that large volume liquid xenon detectors operated in different modes will contribute to answering some of the most fundamental questions in particle physics, astrophysics and cosmology, fulfilling the most demanding detection challenges. From experiments like MEG, currently the largest liquid xenon scintillation detector in operation, dedicated to the rare mu -> e + gamma decay, to the future XMASS which also exploits only liquid xenon scintillation to address an ambitious program of rare event searches, to the class of time projection chambers like XENON and EXO which exploit both scintillation and ionization of liquid xenon for dark matter and neutrinoless double beta decay, respectively, we anticipate unrivaled performance and important contributions to physics in the next few years.

Radiation tolerance of CMOS monolithic active pixel sensors with self-biased pixels

CMOS monolithic active pixel sensors (MAPS) are proposed as a technology for various vertex detectors in nuclear and particle physics. We discuss the mechanisms of ionizing radiation damage on MAPS hosting the dead time free, so-called self bias pixel. Moreover, we introduce radiation hardened sensor designs which allow operating detectors after exposing them to irradiation doses above 1 Mrad.

A 12-bit multichannel ADC for pixel detectors in particle physics and nuclear imaging

Modern pixel detectors in nuclear and particle physics experiments and also in nuclear imaging, starve for highly integrated application specified integrated circuit (ASIC), whereas in China the study of ASIC still stays far away from practical application. The lack of ASIC strictly limits the research and development of domestic high energy physics field. A 12-bit multichannel ADC designed for high density readout is introduced as a major candidate for solution. A precise model is discussed and the simulation fully agrees with the model, which indicates a key principle of design. Design is performed according to the given rule, and novel layout techniques are carried out. Measurement results in all aspects are also obtained, showing an excellent real performance, which satisfies the practical requirement.

Real-time imaging for dose evaluation during antiproton irradiation

Online monitoring of the stopping distribution of particle beams used for radiotherapy provides the possibility of detecting possible errors in dose deposition early during a given treatment session, and may therefore help to improve the quality of the therapy. Antiproton annihilation events produce several long-range secondary particles which can be detected in real time by standard high energy particle physics detector systems. In this note, Monte Carlo calculations are performed in order to study the feasibility of real-time imaging by detecting charged pions produced during antiproton irradiation of typical biological targets. A simple treatment plan in a water phantom is simulated and the results show that by detecting π± the position and the size of the planned target volume can be located with precision in the order of 1 mm.

A Time Projection Chamber with triple GEM and pixel readout

Due to many favorable properties it is very attractive to use Micro Pattern Gas Detectors (MPGDs) as gas amplification stages in Time Projection Chambers (TPCs). Especially the high granularity, intrinsic suppression of ion backflow, high rate capability and almost no distortions due to E × B effects are desirable in future particle physics detectors. To fully exploit the potential of combining MPGDs and TPCs the pad size in the readout plane should be adapted to the structure size of the gas amplification stage. The Timepix chip is well suited for the use as readout chip in gaseous detector by providing metalized pads to pick up the charge. We have constructed a test chamber with a triple GEM and Timepix readout and a maximum drift distance of 26 cm. With this setup we have studied the performance of the detector in various operation environments. Different setups for tests with cosmic rays and for tests in high magnetic fields have been realized. In these environments key detector parameters such as spatial resolution have been studied in dependence on different gas mixtures. We have seen strong evidence for observation of individual electrons and a spatial resolution of down to 80 μm has been measured.

Characterisation of a silicon photomultiplier device for applications in liquid argon based neutrino physics and dark matter searches

The performance of a silicon photomultiplier has been assessed at low temperature in order to evaluate its suitability as a scintillation readout device in liquid argon particle physics detectors. The gain, measured as 2.1 × 106 for a constant over-voltage of 4V was measured between 25°C and -196°C and found to be invariant with temperature, the corresponding single photoelectron dark count rate reducing from 1MHz to 40Hz respectively. Following multiple thermal cycles no deterioration in the device performance was observed. The photon detection efficiency (PDE) was assessed as a function of photon wavelength and temperature. For an over-voltage of 4V, the PDE, found again to be invariant with temperature, was measured as 25% for 460nm photons and 11% for 680nm photons. Device saturation due to high photon flux rate, observed both at room temperature and -196°C, was again found to be independent of temperature. Although the output signal remained proportional to the input signal so long as the saturation limit was not exceeded, the photoelectron pulse resolution and decay time increased slightly at −196°C.

Use of GEANE for tracking in virtual Monte Carlo

The concept of Virtual Monte Carlo (VMC) allows to use different Monte Carlo programs to simulate particle physics detectors without changing the geometry definition and the detector response simulation. In this context, to study the reconstruction capabilities of a detector, the availability of a tool to extrapolate the track parameters and their associated errors due to magnetic field, straggling in energy loss and Coulomb multiple scattering plays a central role: GEANE is an old program written in Fortran 15 years ago that performs this task through dense materials and that is still succesfully used by many modern experiments in its native form. Among its features there is the capability to read directly the geometry and the magnetic field map from the simulation and to use different track representations. In this work we have ‘rediscovered’ GEANE in the context of the Virtual Monte Carlo: we will show how GEANE has been integrated in the FairROOT framework, firmly based on the VMC, by keeping the old features in the new ROOT geometry modeler. Moreover new features have been added to GEANE that allow one to use it also for low density materials, i.e. for gaseous detectors, and preliminary results will be shown and discussed. The tool is now used by the PANDA and CBM collaborations at GSI as the first step for the global reconstruction algorithms, based on a Kalman filter which is currently under development.

The CDF silicon detector: Performance and longevity

The CDF silicon vertex detector is one of the largest operating silicon detectors in particle physics. Its silicon sensors have 722,432 channels readout by 5456 chips and cover an area of 6 m 2 . The detector is used for precision tracking and in the hardware trigger for events with a displaced vertex. This paper includes a brief review of the detector performance and mainly focuses on issues of longevity and effects of radiation damage. An analysis of the time evolution of depletion voltages and signal-to-noise ratios indicates that the CDF silicon detector should outlast the Tevatron Run II without major degradation of performance.

Spin-off from particle detectors in the field of medicine and biology

Since the discovery of X-rays by Roentgen in 1895 physicists have played a major role in the development of medical imaging instrumentation. More recently, the technological developments in several areas of applied physics, the new generation of particle physics detectors and the development of an information-based society all combine to enhance the performance of presently available imaging devices. This paper describes the critical parameters of modern medical imaging in the context of the spectacular development of in-vivo molecular imaging, which will soon allow to bridge post-genomics research activities with new diagnostics and therapeutic strategies for major diseases. In particular, the molecular profiling of tumors and gene expression open the way to tailored therapies and therapeutic monitoring of major diseases like cancer, degenerative and genetic disorders. Moreover, the repeatability of non-invasive approaches allows an evaluation of drug targeting and pharmacokinetics studies on small animals, as well as a precise screening and treatment follow-up of patients. The technical requirements on imaging devices are very challenging but are rather similar in many respects to the ones of modern particle detectors on high-luminosity accelerators. Examples will be given of active technology transfer areas from high-energy physics detectors, which can significantly improve the performance of future medical imaging devices. Special emphasis will be put on the need for a globalization of technology research and development as modern instrumentation in a vast range of applications has similar requirements and spin-off should be more and more understood as cross-fertilization between different disciplines.

Serial powering of silicon strip detectors at SLHC

Serial powering is a technique to power a large numbers of detector modules using a single power cable and a constant current source. Module power is derived using local shunt regulators. Serial powering is of great interest for large-scale silicon tracking detectors for particle physics with many thousands of densely packed detector modules. We have been operating six ATLAS Semiconductor Tracker (SCT) modules using both serial powering and conventional independent powering. The modules operated stably with no indication of any extra noise sources. We present selected results and discuss the system aspects of serial powering.

A monolithic time stretcher for precision time recording

Identifying light mesons which contain only up/down quarks (pions)from those containing a strange quark (kaons) over the typical meterlength scales of a particle physics detector requires instrumentationcapable of measuring flight times with a resolution on the order of20ps. In the last few years a large number of inexpensive,multi-channel Time-to-Digital Converter (TDC) chips have become available.These devices typically have timing resolution performance in thehundreds of ps regime. A technique is presented that is a monolithicversion of ``time stretcher'' solution adopted for the BelleTime-Of-Flight system to address this gap between resolution need andintrinsic multi-hit TDC performance.

Cosmic ray and gamma astrophysics with the AMS-02 experiment

The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to operate on the International Space Station (ISS) for a minimum period of three years. The aim of AMS is the direct detection of charged particles in the rigidity range from 0.5 GV to few TV to perform high statistics studies of cosmic rays in space and a search for antimatter and dark matter. AMS will provide precise gamma measurements in the GeV range. In addition, the good angular resolution and identification capabilities of the detector will allow clean studies of galactic and extra-galactic sources, the diffuse gamma background and gamma ray bursts.

Mega-ton water Cherenkov detectors for particle and astro-particle physics

Physics potential of mega-ton-class water Cherenkov detectors is discussed. Especially, emphasis is made on the non-accelerator physics topics, including atmospheric neutrinos, solar neutrinos, supernova neutrinos and proton decays.

Design and qualification of the AMS-02 flight cryocoolers

Four commercial Sunpower M87N Stirling-cycle cryocoolers will be used to extend the lifetime of the Alpha Magnetic Spectrometer-02 (AMS-02) experiment. The cryocoolers will be mounted to the AMS-02 vacuum case using a structure that will thermally and mechanically decouple the cryocooler from the vacuum case. This paper discusses modifications of the Sunpower M87N cryocooler to make it acceptable for space flight applications and suitable for use on AMS-02. Details of the flight model qualification test program are presented. AMS-02 is a state-of-the-art particle physics detector containing a large superfluid helium-cooled superconducting magnet. Highly sensitive detector plates inside the magnet measure a particle’s speed, mass, charge, and direction. The AMS-02 experiment, which will be flown as an attached payload on the International Space Station, will study the properties and origin of cosmic particles and nuclei including antimatter and dark matter. Two engineering model cryocoolers have been under test at NASA Goddard since November 2001. Qualification testing of the engineering model cryocooler bracket assembly including random vibration and thermal vacuum testing was completed at the end of April 2005. The flight cryocoolers were received in December 2003. Acceptance testing of the flight cryocooler bracket assemblies began in May 2005.

The alpha magnetic spectrometer on the International Space Station

The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to measure charged cosmic ray spectra up to the TV region, with high-energy photon detection capability up to few hundred GeV. AMS is a superconducting spectrometer with large acceptance, long duration (at least three years for the magnet) and state of the art particle identification techniques. AMS will investigate the composition of cosmic rays with high statistics and provide the most sensitive search for the existence of antimatter nuclei and for the nature of dark matter. The detector is being constructed with an eight-layer Silicon Tracker inside a large superconducting magnet, providing a ~0.8 Tm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2 </sup> bending power and an acceptance of ~0.4 m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> sr. A Transition Radiation Detector and a three-dimensional Electromagnetic Calorimeter allow for electron, positron and photon identification, while a Time of Flight scintillating system and a Ring Image Cerenkov detector perform independent velocity measurements. This complex apparatus will identify and measure nuclei up to Iron. We will describe the overall detector construction and performance, which is due to be completed by 2006. The detector will be installed on ISS (International Space Station) in 2008

AMS: A Cosmic Ray Observatory

The Alpha Magnetic Spectrometer (AMS) is a particle physics detector designed to operate in space beyond the earth atmosphere. AMS will measure all the charged cosmic rays and light nuclei spectra in the GV to TV rigidity domain, and high energy cosmic gamma rays as well. With a large acceptance, at least 3 years of observation, and state of the art redundant particle identification techniques, AMS will provide a continuous survey of charged cosmic rays fluxes and the most sensitive search for the existence of anti matter nuclei and for the origin of dark matter. The detector construction will be completed by 2005. AMS should be installed on the ISS (International Space Station) in 2007 and will record several billions cosmic rays per year of operation.