Recoil Detector Research Articles

Angular dependence of theppelastic-scattering analyzing power between 0.8 and 2.8 GeV. I. Results for 1.80–2.24 GeV

Experimental results are presented for the $\mathrm{pp}$ elastic-scattering single spin observable ${A}_{\mathrm{oono}}{=A}_{\mathrm{ooon}}{=A}_{N}=P,$ or the analyzing power, at 19 beam kinetic energies between 1795 and 2235 MeV. The typical c.m. angular range is $60--100\ifmmode^\circ\else\textdegree\fi{}.$ The measurements were performed at Saturne II with a vertically polarized beam and target (transverse to the beam direction and scattering plane), a magnetic spectrometer and a recoil detector, both instrumented with multiwire proportional chambers, and beam polarimeters.

A Recoil Detector for electron scattering experiments with internal targets

A Recoil Detector has been constructed for electron-scattering experiments with gas targets internal to the Amsterdam Pulse Stretcher and storage ring (AmPS) at NIKHEF. The detector was designed to detect low-energy (1–10 MeV/nucleon) and low-mass ( A ≤ 4) recoiling nuclei emerging from electron-induced reactions. It consists of four sensitive elements: a low-pressure two-step avalanche chamber, two layers of silicon strip detectors of 100 and 475 μm thickness, and a scintillator. The signals from the separate detector elements are processed by custom-made analog and digital electronics. The detector was operated successfully at the AmPS electron scattering facility with a gaseous helium target of 10 15 atoms cm −2 internal to the storage ring and beam currents of up to 200 mA.

CHICSi at CELSIUS storage ring

CHICSi is a 3 π multidetector device which will operate in ultra high vacuum (UHV) at the CELSIUS storage ring in Uppsala, Sweden. Some 600 telescopes with very low energy threshold (∼1MeV/nucleon) cover angles > 13°. A recoil detector array and a projectile fragmentation wall are subprojects that will further increase efficiency of CHICSi. The ultimate goal for the physics program of CHICSi is to perform experiments that can provide a better understanding of the nuclear equation of state, especially the liquid-gas phase transition and its connection to the multifragmentation process.

Measurement of the transverse kinetic energies of argon recoil ions produced in 120 MeV $\sf Si^{8+}$ -Ar collisions

Measurements were carried out to deduce the transverse kinetic energies of highly charged argon recoil ions produced in single collisions of 120 MeV ions with argon atoms in which the post collision charge states of the projectiles were not determined. A time of flight spectrometer was designed and fabricated to detect the charge states of recoils. Experimental procedures for optimizing the spectrometer for extraction, transmission and detection of recoils are described. A simple approach for determining the transverse kinetic energy of the recoil ions from FWHM of the peaks is reported. This method is shown to be independent of the choice of collision partners and requires only the knowledge of the physical values of “optimized parameters” of time-of-flight spectrometer used in the experiment. The transverse kinetic energy of the recoil ions determined from the present approach is found to vary from 0.03 eV for to 4.02 eV for Ar10+. These values are compared with the results reported by earlier workers and are shown to follow a q2-behaviour up to a charge state q =8+ of the recoil ions.

Complete angular distribution measurements ofppspin correlation parametersAxx,Ayy,andAxzand analyzing powerAyat 197.4 MeV

Measurements of $\mathrm{pp}$ spin correlation coefficients ${A}_{\mathrm{xx}},$ ${A}_{\mathrm{yy}},$ and ${A}_{\mathrm{xz}}$ and analyzing power ${A}_{y}$ for $\mathrm{pp}$ elastic scattering at 197.4 MeV over the laboratory angular range 3.5 \ifmmode^\circ\else\textdegree\fi{}--43.5 \ifmmode^\circ\else\textdegree\fi{} $({\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}=7\ifmmode^\circ\else\textdegree\fi{}--90\ifmmode^\circ\else\textdegree\fi{})$ have been carried out. The typical statistical accuracy per 1$\ifmmode^\circ\else\textdegree\fi{}$ angle bin is better than 0.02 for the ${A}_{\mathrm{mn}}$ and better than 0.005 for ${A}_{y}.$ Systematic errors are negligible except for an overall normalization uncertainty of 2.5% for ${A}_{\mathrm{mn}}$ and 1.3% for ${A}_{y}.$ The experiment makes use of a polarized hydrogen gas target internal to a proton storage ring (IUCF Cooler) and a circulating beam of polarized protons. The target polarization is switched in sign and direction $(x,y,z)$ every 2 s by reversing a weak guide field $(\ensuremath{\approx}0.3$ mT). Scattered and recoil protons are detected in coincidence by two sets of wire chambers, by scintillators, and by silicon-strip recoil detectors placed 5 cm from the proton beam. Analysis methods and comparison to recent $\mathrm{pp}$ partial-wave analyses and $\mathrm{NN}$ potential models are described.

A recoil detector for the internal target facility of AmPS (NIKHEF)

A recoil detector has been built for internal target experiments with the Amsterdam Pulse Stretcher and storage ring, AmPS, of NIKHEF. The detector was designed to detect low-energy (1–20MeV/nucleon) and low-mass (A≤4) recoiling nuclei emerging from electron-induced reactions. The detector consists of a low-pressure, two-step avalanche chamber, two layers of silicon strip detectors of 100 and 475μm thickness and a scintillator. The signals from the separate detector elements are processed by custom-made analog electronics and dedicated VME-based digitizer modules. The detector was operated successfully at the AmPS electron scattering facility with a gaseous He target of 1015atoms/cm2 internal to the storage ring and beam currents up to 200mA of 660MeV electrons. Unambiguous particle separation was achieved.

The bolometers as nuclear recoil detectors

Our group is involved in experiments using bolometric detectors since ten years for rare event searches like double beta decay or Dark Matter interactions. During last year, to check the quenching factor of TeO2 bolometers, we have measured the nuclear recoils at energy as low as 15keV in our experimental apparatus at Laboratori Nazionali del Gran Sasso. Two 72g TeO2 detectors were exposed under vacuum to a 228Ra α source that implanted on them 224Ra nuclei. The nuclei emitted by the implanted source were detected in one bolometer in coincidence with the corresponding α particles in the other. The energy spectrum of the 103.4keV 224Ra nuclei has been obtained with an energy resolution of about 12keV. Furthermore an α measurement of Roman lead has exploited also the sensitivity of this technique to check for ultralow activity in matter, taking advantage of the source≡detector approach. A limit on the 210Pb contamination in roman lead as low as 4mBq/Kg has been obtained.

Ion beam analysis of oxidised a-C:D layers on Be — A comparison of 4He RBS and 28Si ERD analysis

The composition of intermixed layers on Be containing H, D, Be, C and O has been analysed using conventional 4He RBS at 2.2 MeV together with 2.5 MeV 4He ERD for hydrogen isotope analysis. The results are compared with heavy ion ERD using 12–40 MeV Si incident ions and detection of recoils without mass separation. For the analysis of the RBS and ERD data the newly developed spectra simulation program SIMNRA has been used. The advantages and disadvantages of both methods in respect to depth resolution, data analysis and radiation damage are discussed.

Detection of neutron-induced nuclear recoils in a low-pressure gaseous detector for particle dark matter searches

Recent neutron beam tests of a prototype detector to search for weakly interacting massive particles in the Galactic Halo are presented. The detector is an optically imaged time-projection chamber using various low-pressure gas mixtures. This technique potentially offers significant advantages for the detection of galactic dark matter in that it measures both the energy and direction of the nuclear recoil. In this paper we present measurements of ranges of neutron-induced nuclear recoils in different target gasses which are then used to determine the sensitivity of the device in a dark matter search. We also demonstrate the ability to accurately determine the direction of the recoil which can be used to discriminate signal from background using the expected diurnal modulation in the average recoil direction, which is unique to particle dark matter interactions.

Use of SSNTDs in neutron beam dosimetry

A new Biological Irradiation Facility (BIF) has been constructed at the Budapest Research Reactor Center. The 10 cm diameter beam is led through a variable filter and collimator system, providing different neutron spectra from the nearly pure fission one to a well moderated, 1/E spectrum. To use the irradiator for biological irradiation and for investigating the response of neutron detector materials one must know the neutron spectrum, the beam intensity and profile in advance, and moreover, each irradiation should be adequately monitored to be able to correct the dose conversion factors against the burnup of the fuel, change in the reactor thermal power etc. For the purpose, a set of track detectors were developed. All the detectors are chemically etched and evaluated by a new image analyzer system called VIRGINIA (also presented on this conference). Detectors developed are: CR-39 (TASTRAK) track detectors with proton converter (polyethylene, PE) turning this combination into a threshold detector when applying thin gold foils as proton energy degraders; fission track detectors using depleted uranium and thorium with LEXAN polycarbonate and CR-39 using the 6Li and 10B contents of commercially available TLD materials as alpha converters. We present the basic fundamentals of the proton recoil detector, including the response calculation model.

A theoretical simulation of a superfluid3He-B nuclear recoil detector

It has recently been shown [1] that superfluid3He-B constitutes a practical nuclear recoil detector, with a crude pilot study measuring neutron and gamma events down to ≈1keV. The authors emphasised the preliminary nature of their experiment and went on to suggest that the ultimate sensitivity of the technique could be improved by several orders of magnitude with some simple modifications. In this paper we discuss the results of a computer simulation of the proposed experimental arrangement, which suggests that ≈ eV resolutions may indeed prove feasible.

The detection of low energy neutrons and γ-rays by superfluid 3He, a potential dark matter detector

We have demonstrated in a pilot study using an existing experiment that superfluid He-3 at 100 mu K can be used as a nuclear recoil detector sensitive to neutron and gamma-ray interactions depositing energies down to a few hundred eV. The deposited energy is converted to He-3 quasiparticles which are detected by their effect on a vibrating wire resonator in the liquid. The system can be calibrated independently using a second vibrating wire as a heater but a convenient fixed point is provided by the exothermic reaction n + He-3(2) = p + H-3(1) + 764 keV. Given the great potential for improvement we propose that the system might make a sensitive WIMP detector.

Measurements of the number of neutrons emitted per fission in a fast neutron spectrum for 235U, 237Np, and 243Am

Experiments were designed and performed to determine the number of neutrons emitted per fission, v, for 235U, 237Np and 243Am in a fast neutron spectrum. The neutron emission rates were observed using three proton recoil detectors. The detection system's efficiency was determined using a 252Cf source. The fission rate measurements were performed using solid state nuclear track detectors (SSNTD). The measured values of v in the fast spectrum of the 144 keV silicon-filtered neutron beam for 235U, 237Np, and 243Am are 2.54 ± 0.06, 3.13 ± 0.12, and 4.00 ± 0.35, respectively.

A highly sensitive nuclear recoil detector based on superfluid3He-B

The excitations in superfluid3He have a dispersion curve in which the energy minimum does not coincide with the momentum minimum. As a result, when a mechanical resonator moves through a gas of such excitations, normal and Andreev scattering processes introduce a large asymmetry into the momentum exchange and the mechanical resonator experiences a very large drag force. A gas of such excitations is thus very easy to detect even at very low densities. We have exploited this effect to monitor the increase in excitation density in a small volume caused by a particle interaction. The working volume is filled with superfluid3He-B at around 100 μK. A particle undergoing an interaction in the volume releases a shower of quasiparticle excitations which can be detected by the increase in damping on a vibrating wire resonator. A small hole in the container allows the excitations to leak out into the outside colder liquid to reset the working liquid to the resting state. Using an existing experiment we can detect nuclear recoil interactions depositing energies as low as 500 eV. Two simple modifications should allow us to detect interactions in the 10 eV range.

Potential Dark Matter Detector? The Detection of Low Energy Neutrons by Superfluid 3He.

Using an existing experiment we have demonstrated in a pilot study that superfluid ${}^{3}$He at 100 \ensuremath{\mu}K can be used as a nuclear recoil detector sensitive to neutron and $\ensuremath{\gamma}$ interactions depositing energies down to a few hundred eV. The deposited energy is converted to ${}^{3}$He quasiparticles which are detected by their damping effect on a vibrating wire resonator in the liquid. The system can be calibrated independently but a convenient fixed point is provided by the exothermic reaction $n+_{2}^{3}H\mathrm{e}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}p+_{1}^{3}H+764$ keV. Given the great potential for improvement we propose that the system might make a sensitive weakly interacting massive particle detector.

Determination of Neutron and Photon Dose Equivalent at Workplaces in Nuclear Facilities in Sweden (A joint SSI-EURADOS Comparison Exercise)

The accuracy of the dosimetry (personal and area monitoring) has been investigated inside the containment buildings of two pressurised water reactors and in the environment of a transport cask with spent fuel elements. The dosimetric quantities of main interest were ambient dose equivalent and personal dose equivalent, as operational quantities, and effective dose equivalent, as limit quantity. They were either directly determined by means of instruments and dosemeters or calculated from the experimentally determined directional spectral neutron fluences. Several groups employing different techniques carried out the investigations. The comprehensive comparison exercise has shown that a well specified Bonner sphere spectrometer and a set of proton recoil detectors are well-suited to determine the neutron field for reference purposes. The neutron fields were rather soft with up to 70% of the neutron dose equivalent contributed by neutrons of energies less than 100 keV. On account of their energy dependence, rem counters overestimate, and TEPC systems underestimate, the neutron dose equivalent, even if calibrated in the field of a D2O-moderated 252Cf source. Only a recently developed active dosemeter, based on superheated drop detectors (only used outside the containment), measured the ambient dose equivalent in good agreement with the results obtained with Bonner spheres). Measurements with several personal dosemeters irradiated on a phantom were used to estimate the directional properties of the neutron field. This is required for the calculation of personal and effective dose equivalent values. Some personal dosemeters gave dose equivalent results in satisfactory agreement (±20%) with reference values. In any case the measured dose equivalent values were conservative estimates of the corresponding effective dose equivalent values. The application of the new recommendations of the International Commission on Radiological Protection (ICRP) will result in about 50% higher values of neutron ambient dose equivalent. In the determination of the photon ambient dose equivalent, which amounts to about 30% of the total dose equivalent, differences up to 50% were observed between the readings of GM counters and TEPC's, chiefly caused by high energy photons present in the containment building.

Study of the nucleon density distribution of 6He and 8He by proton elastic scattering in inverse kinematics

Nuclear matter distributions of the neutron-rich nuclei 6He and 8He were studied via proton-nucleus scattering in inverse kinematics using the recoil detector IKAR. The differential cross sections for p 4He and p 8He elastic scattering were measured with un uncertainty of ±2% for the absolute normalization for proton recoil energies from 1 to 20 MeV. The experimental techniques and the data analysis are described and first Glauber calculations presented. Data analysis is still in progress so only preliminary results are given.

Measurement of 14 MeV neutrons at TFTR with Si-diode detectors

A detector system based on partially depleted silicon surface barrier detectors and fast front-end electronics has been built and cross calibrated to a set of absolutely calibrated 4He recoil detectors. The cross-calibration factor for the channel with the widest dynamic range is 2.5×10−13 counts per 14 MeV source neutron. These data agree well with the independent neutron activation data. The new detector system covers a large dynamic range (corresponding to 1013–1018 neutrons/s). The response is linear, except at the highest count rates where the detector dead time (∼200 ns) causes departure from linearity. The noise discrimination against 2.5 MeV neutrons and γ pileup is excellent. Measurements of D-T neutrons from a tritium gas puff experiment as well as from a high-power D-T discharge in the TFTR tokamak are presented.

RBS and recoil spectrometry analysis of CoSi2 formation on GaAs

Mass and energy-dispersive recoil spectrometry has recently reached the state of development where it is possible to separately characterise Ga and As in GaAs samples. Since it is possible to simultaneously characterise several elements (light as well as heavy), e.g. C, O, Si, Co, Ga and As, the technique is suited for examining the depth distribution of metallisation contacts on GaAs. In a Swedish-Australian collaboration a recoil detector telescope was attached to a beamline of the FN tandem accelerator “ANTARES”, at Lucas Heights Research Laboratories, Australia. In the measurements presented here, 127I10+ at an energy of 77 MeV was employed to analyse GaAs samples with thin film overlayers — Si(220 nm)/Co(50 nm)/〈100〉-GaAs. A reference sample and samples annealed at 300 to 600°C were analysed. The measurements showed that CoSi2 is formed during annealing at and above 500°C with no detectable reaction between the GaAs-substrate and the CoSi2 overlayer.

Charged fusion product diagnostics in Alcator C-Mod

With a plasma current of up to 3 MA, toroidal field of up to 9 T, the confinement of the charged fusion products (CFPs) in Alcator C-Mod is expected to be excellent. For example, at maximum current and field, classical losses of the 0.8 MeV 3He, 1 MeV triton, 3 MeV proton, 3.5 and 3.7 MeV alphas are expected to be less than 5%. For the study of the global confinement of CFPs, we plan to measure the burnup of the 1 MeV triton (from the D–D reaction) using a proton recoil detector (NE-213) for the detection of the 14 MeV neutron resulting from the secondary fusion reaction (D–T). On the other hand, loss measurements of CFPs will be made inside the first wall with two detectors (one at the bottom, one at the midplane) using silicon based detectors. The midplane detector will be used to diagnose D–3He plasmas by looking at the unconfined 14.7 MeV proton. In addition to the derivation of fusion yield, energy distribution of the escaping protons will provide information about the ion velocity distribution of the reactants. The bottom detector is time, pitch angle and energy resolved, and thus will be used to study loss mechanisms such as first orbit, toroidal field ripple and magnetohydrodynamics-induced diffusion.