P. De Lurgio

Results from a Search for Light-Mass Dark Matter with a p -Type Point Contact Germanium Detector

We report on several features in the energy spectrum from an ultralow-noise germanium detector operated deep underground. By implementing a new technique able to reject surface events, a number of cosmogenic peaks can be observed for the first time. We discuss an irreducible excess of bulklike events below 3 keV in ionization energy. These could be caused by unknown backgrounds, but also dark matter interactions consistent with DAMA/LIBRA. It is not yet possible to determine their origin. Improved constraints are placed on a cosmological origin for the DAMA/LIBRA effect.

Experimental constraints on a dark matter origin for the DAMA annual modulation effect

A claim for evidence of dark matter interactions in the DAMA experiment has been recently reinforced. We employ a new type of germanium detector to conclusively rule out a standard isothermal galactic halo of weakly interacting massive particles as the explanation for the annual modulation effect leading to the claim. Bounds are similarly imposed on a suggestion that dark pseudoscalars might lead to the effect. We describe the sensitivity to light dark matter particles achievable with our device, in particular, to next-to-minimal supersymmetric model candidates.

Performance evaluation of multi-pixel photon counters for PET imaging

The multi-pixel photon counter (MPPC), also known as the silicon photo-multiplier (SiPM), is a novel, solid-state photodetector that contains an array of Geiger-mode photodiodes (called microcells below) to a gain in range of 105 -106 when operating at a low voltage of 40-70 V. The device also has relatively high photon detection efficiency (PDE) and fast timing response. It is also compact and insensitive to magnetic fields. These properties of the MPPC has recently created substantial interest in using the device for PET imaging. In this paper, we evaluate and compare the performance properties of three designs of 1times1 mm2 MPPC offered by Hamamatsu for use in PET. We examine the gains of devices, and also their energy and timing resolutions when coupled to LYSO.

Production and commissioning of a large prototype Digital Hadron Calorimeter for future colliding beam experiments

A new detector technology is being developed for future colliding beam experiments that is based on the use of fine-grained calorimetry, to optimize the use of Particle Flow Algorithms (PFAs) in measuring hadronic jets. Instead of traditional tower geometry and energy summation from many sampling layers, the new approach measures energy deposition in 1 cm2 cells on each sampling layer using discriminators. Jets are reconstructed using hit patterns from each layer, combined with information from inner tracking and the electromagnetic calorimeter. We have built a 480,000 channel prototype detector that is based on Resistive Plate Chambers (RPCs) to demonstrate this concept. The development is part of the CALICE Collaboration. The readout system uses a 64-channel custom integrated circuit called DCAL to record hits from each cell and apply a global timestamp. The chips mount directly on sophisticated front-end boards that are not only an integral part of the charge collection of the detector chambers, but also incorporate digital signal transmission, clock and control, and power and ground. The readout of data is serial, multiplexed into high-speed serial streams and sent to a “back-end” VME system for time-sorting and higher-level triggering. The system can be operated with an external trigger or be self-triggered, and can produce trigger signals from the front-end chips. The construction, installation, and commissioning of this prototype system is now complete. We have begun a measurement program using a test beam at Fermilab. An overview of the system is described. Experiences in building this large prototype system are reported. Results from the test beam are presented.

An upgraded front-end switching power supply design for the ATLAS TileCAL detector of the LHC

We present the design of an upgraded switching power supply brick for the front-end electronics of the ATLAS hadron tile calorimeter (TileCAL) at the LHC. The new design features significant improvement in noise, improved fault detection, and generally a more robust design, while retaining the compact size, water-cooling, output control, and monitoring features in this 300 KHz design. We discuss the improvements to the design, and the radiation testing that we have done to qualify the design. We also present our plans for the production of 2400 new bricks for installation on the detector in 2013.

A new detector for time-resolved small angle X-ray scattering studies

A new detector for time-resolved small-angle X-ray scattering has been designed and built for experiments at the Advanced Photon Source of Argonne National Laboratory. This detector is made from a 500 mum thick by 150 mm diameter ultra-high purity silicon wafer, which directly converts X-rays into electron-hole pairs. The electrodes are concentric rings that integrate the scattered X-rays over the azimuthal angle. The widths of the rings are optimized for the size of the X-ray beam and its energy spread. Only 128 rings, or channels, are needed to measure a scattering profile. The read-out electronics consist of preamplifiers with pulse-shaping, which are mounted on the detector, and 12-bit, 20 MHz digitizers. The resolving time of the electronics is 300 ns, which is sufficient to isolate a single pulse of scattered X-rays when the synchrotron is operated with a hybrid or asymmetric fill pattern. The data acquisition hardware can average a programmable number of digital samples, up to 64, every 3.68 mus (the period of the synchrotron) to provides a single 12-bit average of the voltage from the analog amplifier chain. The temporal range of the detector is 3.68 seconds or longer and may be controlled by the experimenter. An alpha source is used to calibrate the detector and electronics, and document their performance. Preliminary results obtained during the commissioning of the detector are presented

Single Event Upset energy dependence in a buck-converter power supply design

We present a study of Single Event Upsets (SEU) performed on a commercial pulse-width modulator controller chip for switching power supplies. We performed tests to study the probability of an SEU occurring as a function of incident particle (hadron) energy. We discuss the performance of the circuit, and present a solution using external circuitry to effectively eliminate the effect.

2-D scintillation position-sensitive neutron detector

A new 2-dimensional scintillation position-sensitive neutron detector (PSND) with an active area of 155times155 mm2 was developed for use on the single crystal diffractometer at the intense pulsed neutron source at Argonne National Laboratory. The detector is based on the well-proven Anger camera technique and uses a 6Li glass scintillator as the neutron converter. This PSND incorporates a 6times6 PMT array with 29.6 mm pitch and optimized optics to achieve an average spatial resolution of 1.75 mm full width at half maximum. The detector read-out has separate electronics for each PMT and the neutron position is calculated by a microprocessor during acquisition. A newly developed position extraction algorithm makes use of an analytical calculation to determine the event position. This new method improves the linearity of the calculated position, provides a slight improvement in resolution, and in principle allows for the correct determination of position to the edge of the scintillator. The design of the detector enclosure allows multiple detectors to be tiled with minimal dead space between them. In addition, the design incorporates a means of attaching external shielding plates that minimizes the shielding surface area required

A wireless power and data acquisition system for large detectors

A new prototype wireless data acquisition system has been developed with the intended application to read-out instrumentation systems having thousands of channels. The data acquisition and control is based on a compliant implementation of 802.11 based hardware and protocols. Our case study is for a large detector containing photomultiplier tubes. The front-end circuitry, including a high-voltage power supply is powered wirelessly thus creating an all-wireless detector readout. The bench marked performance of the prototype system and how a large scale implementation of the system might be realized are discussed.