Fabrication and performance of a multistrip silicon detector for low energy nuclear experiments

A multistrip silicon detector was fabricated by using planar techniques. It consisted of five parallel pn-junction strips on a wafer of 200 μm thick. The dimension of each strip was 2 mm × 20 mm and the strip pitch was 2.6 mm. The detector was tested by using heavy ions produced in the reaction of ¹⁸¹Ta + ¹⁴N at 210 MeV. We found that it enables clear particle identification for heavy ions and that it shows good property for a position sensitive detector. We studied phenomena of multiple output events induced by a single particle entering the detector; events giving double outputs occurred only in a arrow gap between adjacent strips. Events with more than triple outputs did not exist and insensitive areas were not observed.     

Development of integrated ΔE-E silicon detector telescope using silicon planar technology

An integrated ΔE-E silicon detector telescope using silicon planar technology has been developed. The technology developed is based on standard integrated circuit technology and involves double sided wafer processing. The ΔE and E detectors have been realized in a PIN configuration with a common buried N⁺ layer. Detectors with ΔE thicknesses of 10, 15 and 25 μm, and E detector with thickness of 300 μm have been fabricated and tested with alpha particles using ²³⁸Pu-²³⁹Pu dual alpha source. The performance of the detector with ΔE detector of thickness 10 μm and E detector of thickness 300 μm has been studied for identification of charged particles using 12 MeV ⁷Li⁺ ion beam on carbon target. The results of these tests demonstrate that the integrated detector telescope clearly separates the charged particles, such as alpha particles, protons and ⁷Li. Due to good energy resolution of the E detector, discrete alpha groups corresponding to well known states of ¹⁵N populated during the reaction could be clearly identified.     

A new multidetector system with magnetic spectrograph for study of cosmic ray extensive air shower components

An array of detectors for simultaneous observation of different components of cosmic ray extensive air showers (EAS) is described. The detector array, comprising plastic scintillation counters as electron detectors, magnetic spectrograph units and a muon flash tube chamber as muon detectors and a large volume multiplate cloud chamber as hadron detector has been set up and is now being operated at NBU campus. The array of detectors is sensitive to air showers initiated by cosmic primaries of energy in the range 10¹⁴–10¹⁵ eV.     

Application of CLTD’s for High Resolution Mass Identification and for Stopping Power Measurements of Heavy Ions

An array of calorimetric low temperature detectors (CLTD’s) for energy sensitive detection of heavy ions was combined with time-of-flight (TOF) detectors to obtain a detector system for high resolution mass identification of low energy heavy ions. In addition the same setup was used to prove the ability of CLTD’s to be used in electronic stopping power measurements for heavy ions in matter. Experiments with 50?MeV ⁶³Cu and ⁶⁵Cu ions at the tandem accelerator at the MPI at Heidelberg, and with 25 to 250?MeV ²³⁸U ions at the UNILAC accelerator at GSI at Darmstadt have been performed. For ^63,65Cu at 50?MeV a mass resolution of Δm(FWHM)=0.9?amu, and for ²³⁸U in an energy range of 65 to 150?MeV a resolution of Δm(FWHM)=1.28?amu, was obtained. The results for stopping powers of ²³⁸U in carbon and gold are presented and compared with theoretical predictions and data from the literature.     

Test beam results of Current Injected Detectors (CID) irradiated up to 5×10 1 MeV neq/cm

Two full size strip detectors were investigated in this study: one with p⁺ strips (p⁺/n⁻/n⁺) and another with n⁺ strips (n⁺/p⁻/p⁺). Both detectors, are made of magnetic Czochralski silicon (MCz-Si) and irradiated to S-LHC fluencies, were tested with 225 GeV muon beam in the CERN H2 area. The Current Injected Detector (CID) sensors were operated in a cooling box capable of providing a −53 °C temperature. Results indicate a relative charge collection efficiency (CCE) at 5×10¹⁵ n_eq/cm² above 30% in irradiated p⁺/n⁻/n⁺ CID detector at 600 V bias voltage. The signal to noise ratio of this CID module was about eight and a forward current of 30 μA was needed for detector biasing. In standard reverse bias, the same detector could not provide a sufficiently large signal for particle tracking purposes. A p-type (n⁺/p⁻/p⁺) sensor was irradiated to a fluence of 2×10¹⁵ n_eq/cm² and measured under the same test beam conditions. According to the theory of CIDs developed by the CERN RD39 Collaboration, this detector module could be biased up to only 230 V due to the low irradiation fluence. The CCE at 230 V was 35% in CID operation and 20% when reverse biased.     

Characterization and improvement of thin natural diamond detectors for spectrometry of heavy ions below 1 MeV/amu

In our previous paper [V.Kh. Liechtenstein, N.V. Eremin, R. Golser, W. Kutschera, A.A. Paskhalov, A. Priller, P. Steier, Ch. Vockenhuber, S. Winkler, Nucl. Instr. and Meth. A 521 (2004) 203], first results on the evaluation of thin natural diamond-based detectors (NDDs) as an energy spectrometer for heavy ions in the energy range below 1 MeV/amu were presented. Although results were promising, the energy resolution of the detector was limited by an unexpected high-energy loss in the “dead layer” of the entrance window. In this paper, we report a significant improvement in the spectrometric properties of two highly selected and carefully treated NDDs with electrical contacts made of carbon and gold films as thin as about 10 and 20 μg/cm², respectively, instead of much thicker aluminum contacts used before. In particular, for the NDD with thin carbon contact an energy resolution of 7.6% for ¹⁹⁷Au-ions at 20.6 MeV was obtained. The energy cut-off of the detectors was reduced to 0.9 and 1.5 MeV for carbon and gold contact, respectively. The measured data on energy cut-off for different projectiles are compared with calculations, which yields an estimate of the thickness of the dead layers. Long-term irradiation runs proved stable spectroscopic performance of the detectors, in spite of the inherent “pumping” effects and imperfections of pulse height distributions. Our data suggest that NDD-based spectrometers might outperform other detector types in applications where very fast detectors with high radiation tolerance are required.     

H+ and He+ spectroscopy using silicon pin photodiodes

Silicon PIN photodiodes have been used in detecting H⁺ and He⁺ ions from a 1 MeV accelerator. Energy resolutions (FWHM) from 2.0 keV (at 16 keV) to 4.7 keV (at 1 MeV) for H⁺ and from 3.4 keV (at 22 keV) to 9.8 keV (at 700 keV) for He⁺ have been measured at room temperature. Resolution measurements over this energy range using a premium PIPS detector have also been performed. A comparison between the two detectors shows that the photodiodes exhibit better energy resolution over the whole energy range for H⁺, and comparable resolution for He⁺. It is argued that the resolution of the photodiode can be further improved by manufacturing a device with thinner entrance window.     

First Experiments Aiming for Precise Lamb Shift Measurements on Hydrogen-Like Heavy Ions with Low Temperature Calorimeters

The precise determination of the Lamb shift in hydrogen-like heavy ions provides a sensitive test of quantum electrodynamics in very strong Coulomb fields, not accessible otherwise. To increase the accuracy of the Lamb shift measurement on stored heavy ions at the ESR storage ring at GSI, a calorimetric low temperature detector for hard X-rays was developed. A prototype array consisting of 8 pixels with silicon thermistors and Sn or Pb absorbers was applied in first experiments with stored ²³⁸U⁹¹⁺ and ²⁰⁷Pb⁸¹⁺ ions interacting with an internal gas-jet target. In both experiments the Lyman-α lines were, for the first time by using calorimetric low temperature detectors, clearly identified in clean, almost background-free spectra. A total detection efficiency of 1×10⁻⁷ for the Lyman-α lines was reached and an energy resolution of 115 eV was obtained under the present experimental conditions, which corresponds to a considerable improvement of about half an order of magnitude if compared to conventional Ge semiconductor detectors. Finally preliminary results of the data analysis and future perspectives are discussed.      

Effect of ion implantation on thin hard coatings

The surface mechanical properties of thin hard coatings of carbides, nitrides and borides deposited by r.f. sputtering were improved after deposition by ion implantation. The thickness and the stoichiometry of the films were measured by Rutherford backscattering spectrometry and nuclear reaction analysis before and after ion bombardment. The post ion bombardment was achieved with heavy inert ions such as Kr⁺ and Xe⁺ with an energy sufficient to penetrate the film and to reach the substrate. Both the film adhesion and the microhardness were consistently improved. In order to achieve a more detailed understanding, Rb⁺ and Ni⁺ ions were also used as projectiles, and it was found that these ions were more effective than the inert gas ions.     

Scintillating Bolometers for Double Beta Decay Search

In the field of Double Beta Decay searches the possibility to have high resolution detectors in which a very large part of the natural background can be discriminated with respect to the tiny expected signal, results very appealing. This very interesting possibility can be fulfilled in the case of a scintillating crystal bolometer containing a DBD emitter whose transition energy exceeds the one of the natural 2615 keV gamma line of ²⁰⁸Tl. We present the results achieved in the development of bolometric light detectors for double beta searches. The detectors are 1 mm thick germanium disk coated with a layer of SiO₂ in order to increase the light collection. The adopted temperature sensors are NTD Ge thermistors optimized to work at temperatures between 9 and 13 mK. A light detector with a considerable large area (35 cm²) was constructed and run in a test measurement. A 140 g CdWO₄ crystal (¹¹⁶Cd has a DBD transition energy of 2802 keV) was operated as bolometer and the scintillation light was read by the light detector. The excellent results combined with extreme easy light detector assembly represent the first tangible proof demonstrating the feasibility of this kind of technique.      

Optimization of Geomagnetic Shielding for MKIDs Mounted on a Rotating Cryostat

Superconducting detectors, such as microwave kinetic inductance detectors (MKIDs), are sensitive to the effects of ambient magnetic fields. There are two effects magnetic fields have on the response of MKIDs; the trapping of magnetic fields inside the superconducting materials degrades the resonator quality, and the time variation of the magnetic fields results in a baseline fluctuation. In the case of radio astronomy, this means the detector must be protected from the geomagnetic field. Here, we construct a test system to evaluate the effects described. We also evaluate the impact of the magnetic shield. We find that a shielding power of 47 dB is necessary in the case of application with a noise equivalent power of \(2.4 \times 10^{-16}\,\text {W}/\sqrt{\text {Hz}}\). We also confirm that the measured shielding power obtained using permalloy films is consistent with simulations based on the finite element method to an accuracy of 1 dB. We have designed magnetic shields for the GroundBIRD CMB telescope using these results. We achieve a sufficient shielding power of 55 dB.     

Microfabrication of Transition-Edge Sensor Arrays of Microcalorimeters with <Superscript>163</Superscript>Ho for Direct Neutrino Mass Measurements with HOLMES

HOLMES is aiming at a direct measurement of neutrino mass by performing a calorimetric measurement of the energy released in the decay of ¹⁶³Ho. In such approach, the ¹⁶³Ho source, with the required activity, needs to be embedded in the detector. HOLMES will deploy a large array of transition-edge sensor microcalorimeters with implanted ¹⁶³Ho ions. While good progress has been made in optimizing single pixel design and fabrication to achieve the target resolution, a major challenge is the fabrication of arrays of such microcalorimeters with the required amount of ¹⁶³Ho ions embedded in the detectors absorber. We describe the multi-step microfabrication process implemented to produce the detector arrays for HOLMES. One crucial part of such process is the ability to perform co-deposition of gold during the ¹⁶³Ho implantation process on the detectors absorber. We describe the UHV target chamber, with integrated gold deposition system, we have built to achieve this goal.     

Introduction of high oxygen concentrations into silicon wafers by high-temperature diffusion

The tolerance of silicon detectors to hadron irradiation can be improved by the introduction of a high concentration of oxygen into the starting material. High-resistivity Floating-Zone (FZ) silicon is required for detectors used in particle physics applications. A significantly high oxygen concentration (>10¹⁷ atoms cm⁻³) cannot readily be achieved during the FZ silicon refinement. The diffusion of oxygen at elevated temperatures from a SiO₂ layer grown on both sides of a silicon wafer is a simple and effective technique to achieve high and uniform concentrations of oxygen throughout the bulk of a 300 μm thick silicon wafer.     

Sensitive and Stable 2D Perovskite Single-Crystal X-ray Detectors Enabled by a Supramolecular Anchor

Perovskite X-ray detectors have been demonstrated to be sensitive to soft X-rays (<80 keV) for potential medical imaging applications. However, developing X-ray detectors that are stable and sensitive to hard X-rays (80 to 120 keV) for practical medical imaging is highly desired. Here, a sensitive 2D fluorophenethylammonium lead iodide ((F-PEA)₂PbI₄) perovskite single-crystal hard-X-ray detector from low-cost solution processes is reported. Dipole interaction of organic ions promotes the ordering of benzene rings as well as the supramolecular electrostatic interaction between electron-deficient F atoms with neighbor benzene rings. Supramolecular interactions serve as a supramolecular anchor to stabilize and tune the electronic properties of single crystals. The 2D (F-PEA)₂PbI₄ perovskite single crystal exhibits an intrinsic property with record bulk resistivity of 1.36 × 10¹² Ω cm, which brings a low device noise for hard X-ray detection. Meanwhile, the ion-migration phenomenon is effectively suppressed, even under the large applied bias of 200 V, by blocking the ion migration paths after anchoring. Consequently, the (F-PEA)₂PbI₄ single crystal detector yields a sensitivity of 3402 μC Gy⁻¹air cm⁻² to 120 keV_p hard X-rays with lowest detectable X-ray dose rate of 23 nGy_air s⁻¹, outperforming the dominating CsI scintillator of commercial digital radiography systems by acquiring clear X-ray images under much lower dose rate. In addition, the detector shows high operation stability under extremely high-flux X-ray irradiation.     

Performance of the ALEPH detector at LEP

The performance of the ALEPH detector at the LEP e⁺e⁻ collider is reviewed. The accuracy of the tracking detectors to measure the impact parameter and momentum of charged tracks is specified. Calorimeters are used to measure photons and neutral hadrons, and the accuracy obtained in energy and angle is given. An essential property of the detector is its ability to identify particles; the performance in identification of electrons, muons, neutrinos (from missing energy), charged hadrons, π⁰'s and V⁰'s is described.     

Si(Li)NaI(Tl) sandwich detector array for measurements of trace radionuclides in soil samples

An ultra-sensitive X/γ-ray detector system for assaying trace radioactivity in actinide contaminated soil and ash samples has been developed. The new system consists of an array of 6 large Si(Li) X-ray detectors sensitive on both faces and mounted on edge in a paddle-shaped cryostat with a 14 cm diameter Be window on each side. The paddle, with a sample of the soil placed at each window, is sandwiched between 2 large NaI(Tl) scintillators which suppress the γ background. With X-rays being measured simultaneously from soil in 2 sample holders and background reduced by 50% using anticoincidence, the sensitivity of this detector is 4 times higher than that of conventionally mounted Si(Li) detectors. A soil sample containing 50 pCi/g ²³⁹Pu was measured in 5 min with an uncertainty of < 20% and a sample containing 7 pCi/g was measured in 1 h. With fwhm resolution of 400 eV at 17 keV, the ULβ₁ and NpL_β1 X-ray peaks are resolved thus permitting measurement of trace Pu in the presence of ²⁴¹Am. This is the most sensitive and selective detector known for nondestructive assay of radioactivity in soil and other samples.     

Construction and properties of a gamma-ray detector based on D(γ, n)H neutron counting

The photodisintegration of deuterium with subsequent neutron counting has been used in a system to detect high-energy γ-rays. The system consists of a cylindrical tank filled with 242 l of heavy water and surrounded by 30 ³He-filled proportional counters. Details of the construction, specifications and characteristics of the detector are described. The detector has been used to measure the hexadecapole strength of the 2506 (J^π = 4⁺) → 0 (J^π = 0⁺) keV γ-ray transition in ⁶⁰Ni (E4 = 78 nuclear physics applications, it is proposed that the detector be used for studies relevant to nuclear astrophysics, in particular for the study of capture reactions induced on highly radioactive targets (up to about 1 Ci). The detector is also useful for neutron work (18% neutron efficiency).     

On the dose response of some CVD diamond thermoluminescent detectors

The linearity of dose response of chemical vapour deposition (CVD) diamonds grown at the Institute for Materials Research at Limburg University, Belgium, was investigated over a dose range relevant for radiotherapy. The following CVD diamonds were investigated: (1) a batch of square 3 x 3 mm2 detectors cut from a CVD wafer and (2) an as-grown CVD wafer of 6 cm diameter. A total of 20 CVD square detectors were irradiated with 137Cs gamma rays over the dose range from 200 mGy to 25 Gy. The CVD wafer, used as a large-area thermoluminescent (TL) detector, was exposed to a 226Ra needle. Very few square detectors showed linearity over a limited dose range, followed by saturation of the TL signal. The dose range of linearity was found to be strongly affected by the thermal annealing procedure of the detector. Owing to its high sensitivity and homogeneity of response, the large CVD diamond wafer was found to be very suitable as a large-area detector for 2-D dose mapping of the 226Ra brachytherapy source, possibly for Quality Assurance purposes.     

An on-line tritium-in-water monitor

The paper describes the development and operation of a continuous on-line tritium-in-water monitor for the detection of heavy water leaks into the secondary coolant light water of a heavy water power reactor. The heart of the instrument is its plastic scintillator sponge detector, made from 5 μm thick plastic scintillator films. The sponge weighs only about 1 g and is in the form of disc of 48 mm diameter and 8 mm thickness. The total surface area of the films is about 3000 cm². In the coincidence mode of counting, the detector gives 1000 cps for the passage of 3.7 × 10⁴ Bq/cm³ (1 μCi/cm³) of tritiated water. The background in 6 cm thick lead shielding in the laboratory is 0.2 cps, and inside the reactor building it is below 1 cps. The monitor presently scans 18 sample lines in sequence for 5 min each and gives a printout for the activity in each line.     

Background events in the energy region below 4 MeV detected with a 208 cm3 intrinsic germanium detector: I. Characteristic γ-radiation

A detailed study of the events recorded with a 208 cm³ intrinsic germanium γ-ray detector produced by interactions of natural environmental radiation was undertaken. In the first part of this work, the data on events from characteristic radioactivity are analysed to optimise the shielding requirements for reducing the γ-ray background as seen by the detector. A thickness of 15 cm of Pb all around the detector in the laboratory location, or only 5 cm in the underground location at the mine, is found to be sufficient to attenuate the event rates from environmental characteristic γ-rays to less than the event rates from intrinsic contamination of the detector components in the detector assembly. The salt mine is found to be a natural environment low in γ-ray background.