The use of CsI(Tl) scintillators with photodiode readout in heavy ion experiments

The performance of a ΔE−E telescope consisting of transmission silicon detector and CsI(Tl) scintillators with photodiode read out investigated in 46.7 MeV/u ¹²C induced reaction. The zero-crossing technique of pulse shape analysis has been employed to identify the light charged particles (p, d, t, ) with a low energy threshold, and a detector array composed of nine elements of CsI(Tl) scintillators with photodiode readout have been developed to measure the light charged particle interferometry in intermediate energy heavy ion induced reaction.     

ΔE−E Telescope systems for detecting charged particles produced with a “white” neutron beam

Highly stable ΔE−E telescope systems consisting of plastic scintillation detectors are operated as flux monitors in a “white” neutron beam between 15 and 50 MeV. Multiple telescope systems consisting of large area silicon ΔE detectors and NaI E detectors are set up in a scattering chamber to investigate charged particle reactions induced by fast neutrons up to 50 MeV.     

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.     

Mass resolution of recoil fragment detector telescopes for 0.05–0.5 A MeV heavy recoiling fragments

The factors governing the mass resolution for 0.05–0.5 A MeV recoil nuclei have been investigated for detector telescopes in which carbon-foil time zero detectors and ion-implanted silicon detectors are used to determine the time of flight and energy respectively. Experimentally determined second moments of the mass distribution have been compared with theoretical estimates based on literature data. The experimental mass resolution is in reasonably good absolute agreement with theoretical estimates. For low energy (< 0.3 A MeV) particles the mass resolution is dominated by the contribution from the silicon detector and thus largely independent of timed flight length. In fact for detection of very low energy (0.1 A MeV) recoil nuclei timed flight lengths of less than 0.22 m are sufficient.     

Radiomicroscopy

A nondestructive method and appropriate equipment are described for estimations of microdistribution of radiotracers emitting charged particles within planar transparent or nontransparent samples. The silicon microdetector enables spectrometric measurements (energy resolution 8 keV for 5.485 MeV alpha particles at 293 K) within chosen sites of the analysed sample with high topographic resolution. The method has been applied for beta tracers in life science (e.g. ¹⁴C, ³²P).     

Z-identification of charged particles by signal risetime in silicon surface barrier detectors

The risetimes of the signals collected from totally depleted silicon surface barrier detectors have been measured and show strong dependence on the Z of the incident charged particles. This dependence has been observed for incident ions ranging from tritons to fluorine. A simple theoretical model has been used to predict the observed risetimes for ions whose range is long compared to the diameter of the ionization column which they produce in silicon. For particles with ranges short compared to the depletion depth of the detector it is found that the Z-dependence can be enhanced by allowing these ions to enter through the rear face of the totally depleted detector. For hydrogen and helium ions the dependence of the risetime on the mass M of the ion is also observed.     

CHICSi—a compact ultra-high vacuum compatible detector system for nuclear reaction experiments at storage rings. II. Detectors

We describe the detectors for identification of charged particles and fragments in CHICSi, a large solid angle multi-telescope system mounted inside an ultra-high vacuum (UHV), cluster-jet target chamber. CHICSi performs nuclear reaction experiments at storage rings. The telescopes consist of a first very thin, 10–14 μm Si detector, a second 300 μm (or possibly 500 μm) ion implanted Si detector supplemented by a 6 mm GSO(Ce) scintillator read out by a photodiode (PD) or by a third 300 μm Si detector. The telescopes provide full charge separation up to Z=17 and mass resolution up to A=9 in the energy range 0.7–60A MeV. The thin p-i-n diode detector, etched out from a 280 μm Si wafer, and the GSO/PD detector, both exclusively developed for CHICSi, provide an energy resolution 8%, while the standard 300 μm detectors have 2% energy resolution. Radiation stability of the Si detectors is confirmed up to an integrated flux of 10¹⁰ alpha particles. The GSO detector has 70% light collection efficiency with the optical coupling to the PD a simple open, 0.2 mm, gap. A new method, developed to perform absolute energy calibration for the GSO/PD detector is presented.     

CD: A double sided silicon strip detector for radioactive nuclear beam experiments

A very compact double sided silicon strip detector array is described, designed for use in reaction studies involving radioactive nuclear beams. It is small enough to fit inside a large solid angle γ-detector array and will enable Doppler-shift corrections at energies in the vicinity of the Coulomb barrier. The detector provides sufficient energy and time-of-flight resolution for the identification of light reaction products and can be set up to cover a substantial part of the scattering angular distribution with good resolution.

The device is available in thicknesses of up to 500 μm to stop all interesting reaction products. Moreover, a very thin (35–40 μm) variant of this detector is described that can be used as an energy loss detector in a ΔE−E telescope geometry followed by a detector that measures the residual energy. This provides additional particle identification capabilities, e.g. in light exotic nuclei induced reactions. First results from a commissioning run using a post-accelerated radioactive beam are presented.     

A detector of superhard photons using aligned single crystals

The effects of considerable amplification of the pair production by photons and of radiation of charged particles in aligned single crystals are suggested to use for the creation of a comparatively simple ultrahigh-energy photon detector (ω < 100 GeV) with high angular resolution.     

A position sensitive ionisation chamber for measurement of fission fragments and medium mass heavy ions

A position sensitive ionisation chamber telescope is described with ΔE_gas---E_gas sections which can measure simultaneously the specific energy loss ΔE, energy E and the position of heavy ion reaction products in the median plane. The position information is derived by having a split ΔE structure and by adopting the pulse division method for the signals collected by the two ΔE sections. For on-line angle calibration, the E-part of the anode structure is also split into five segments. The detector was tested with fission fragments from a ²⁵²Cf spontaneous fission source and with heavy ions from the pelletron tandem accelerator. Simultaneous measurement of ΔE and E gives good separation for heavy and light fission fragment groups. The position resolution is found to be 1.1 mm for fission fragments. The detector has been used in heavy ion reaction studies for measuring fission fragments, providing good separation from projectile-like particles.     

A time-of-flight telescope for charged particles produced in neutron-induced reactions

A counter telescope has been developed for the study of neutron-induced charged-particle-producing reactions. This spectrometer differs from those conventionally used for such studies in that it has a flight path long enough (2 m) to allow a fairly accurate energy determination. The use of a pulsed beam with such a spectrometer permits the particle energy to be determined in two ways: from the signal produced by the E counter and from the time-of-flight. This redundancy allows a reduction in background relative to the typical telescope if we demand consistency in the two values for a pulse to be accepted. In addition, the velocity determination through time-of-flight makes a better energy resolution possible than would normally be possible for low-energy charged-particles detected in a scintillator.     

A 5 in. Si(Li)/Pb sampling calorimeter telescope for observation of cosmic gamma rays in the GeV region

A 5 in. diameter Si(Li)/Pb sampling calorimeter with a depth of 28 radiation lengths (30 unit cells × 0.93 radiation lengths) has been constructed. The energy and angular resolutions of the calorimeter have been investigated using CERN SPS positron beams with energies of 10 to 147.8 GeV. The calorimeter shows good linearity over this energy region and the energy resolution is expressed well by σ_E (rms)/E = (16.9 ± 0.9)%/ √E[GeV], where E represents the incident beam energy. The angular resolution of the calorimeter for a single event is 0.3° (rms) at 80 GeV/c. The agreement between these results and Monte Carlo simulations is good.

We are showing a new design of the Si(Li)/Pb sampling calorimeter telescope (SSCT) with an angular resolution (point source localization capability) of about 0.04° (rms) for bright galactic gamma-ray sources. We believe that this telescope is a suitable detector for future observations of cosmic gamma rays in the GeV region, especially when used to search for point sources.     

A test experiment with atmospheric Cherenkov light

A test experiment on atmospheric Cherenkov light was performed to prepare for the setup of a large multimirror gamma-ray telescope. An array of four 1.5 m searchlight mirrors equipped with 5 in. photomultipliers was operated in the fast timing mode. A timing resolution of 0.73 ns rms was measured which corresponds to an angular resolution of 0.38° for vertically incident showers. The transmission factors of BG24 Schott filters were also measured for Cherenkov and night-sky lights with values of 0.64 and 0.25 respectively.     

Spectator detection for the measurement of proton–neutron interactions at ANKE

A telescope of three silicon detectors has been installed close to the internal target position of the ANKE spectrometer, which is situated inside the ultra-high vacuum of the COSY-Jülich light-ion storage ring. The detection and identification of slow protons and deuterons emerging from a deuterium cluster-jet target thus becomes feasible. A good measurement of the energy and angle of such a spectator proton (p_sp) allows one to identify a reaction as having taken place on the neutron in the target and then to determine the kinematical variables of the ion–neutron system on an event-by-event basis over a range of c.m. energies.

The system has been successfully tested under laboratory conditions. By measuring the spectator proton in the pd→p_spdπ⁰ reaction in coincidence with a fast deuteron in the ANKE Forward Detector, values of the pn→dπ⁰ total cross-section have been deduced. Further applications of the telescope include the determination of the luminosity and beam polarisation which are required for several experiments.     

Silicon beam telescope for CMS detector tests

A beam telescope providing precision track measurements as reference for other detectors has been upgraded in the CERN H2 test beam. The apparatus was completely rebuilt from the detector wafers and front-end electronics to the data acquisition system. The new detector setup consists of eight 5.6×5.6 cm² sized DC coupled silicon microstrip detectors. Typical position resolution values of about 7.5 μm were measured. Details of the setup are described and results from the recent beam tests are reported.     

光学综合口径望远镜设计方案讨论

本文提出新建一台4.3米光学、红外新技术望远镜。并与现有北台的几台望远镜用光纤联机提高集光能力达5.1米口径。将4.3米与2.16米望远镜用真空管道联机集像作CCD照相和光干涉测量,提高分辨率达10余米口径。     

Observation of a triple correlation in ternary fission: is time reversal invariance violated?

In ternary fission, besides the two main fission fragments, a third (usually light) charged particle is emitted. A triple correlation has been studied involving the momenta for a specific fission fragment , the momenta of the ternary particle and the spin of the polarized cold neutron inducing fission . The correlation observable reverses sign upon time reversal and thus a non-vanishing value for the expectation value B could possibly be due to TRI being violated. However, final-state interactions or specific properties of the emission mechanism for ternary particles could equally well lead to a non-zero B with TRI being perfectly conserved. The reaction chosen was ²³³U(n,f). An unexpectedly large correlation was observed. From the raw data the value for B is B=−(0.78±0.02)×10⁻³ with the sign corresponding to light fragments. Corrections for neutron polarization, geometric efficiency, resolution of detectors and background increase this figure by a factor of (1.5±0.3).     

A silicon active target for charm particle identification

A silicon active target has been realized to reconstruct with high efficiency the primary vertex of heavy flavour photoproduction events in experiment E687 at the FNAL tevatron. The target is a telescope of 48 layers divided in 4 elements each, giving a total of 192 electronic channels read out with a preamplifier, an amplifier and a charge integrating ADC. The efficiency of the detector in identifying primary vertices has been measured to be 80%, while the longitudinal resolution turned out to be σ 340 μm. Its level of performance allowed the use of the target as a powerful tool to select heavy quark events.     

Space radiation measurements on-board ISS--the DOSMAP experiment

The experiment 'Dosimetric Mapping' conducted as part of the science program of NASA's Human Research Facility (HRF) between March and August 2001 was designed to measure integrated total absorbed doses (ionising radiation and neutrons), heavy ion fluxes and its energy, mass and linear energy transfer (LET) spectra, time-dependent count rates of charged particles and their corresponding dose rates at different locations inside the US Lab at the International Space Station. Owing to the variety of particles and energies, a dosimetry package consisting of thermoluminescence dosemeter (TLD) chips and nuclear track detectors with and without converters (NTDPs), a silicon dosimetry telescope (DOSTEL), four mobile silicon detector units (MDUs) and a TLD reader unit (PILLE) with 12 TLD bulbs as dosemeters was used. Dose rates of the ionising part of the radiation field measured with TLD bulbs applying the PILLE readout system at different locations varied between 153 and 231 microGy d(-1). The dose rate received by the active devices fits excellent to the TLD measurements and is significantly lower compared with measurements for the Shuttle (STS) to MIR missions. The comparison of the absorbed doses from passive and active devices showed an agreement within +/- 10%. The DOSTEL measurements in the HRF location yielded a mean dose equivalent rate of 535 microSv d(-1). DOSTEL measurements were also obtained during the Solar Particle Event on 15 April 2001.