Showing papers in "Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment in 2002"

The BABAR detector

Abstract: BABAR, the detector for the SLAC PEP-II asymmetric e+e- B Factory operating at the upsilon 4S resonance, was designed to allow comprehensive studies of CP-violation in B-meson decays. Charged particle tracks are measured in a multi-layer silicon vertex tracker surrounded by a cylindrical wire drift chamber. Electromagentic showers from electrons and photons are detected in an array of CsI crystals located just inside the solenoidal coil of a superconducting magnet. Muons and neutral hadrons are identified by arrays of resistive plate chambers inserted into gaps in the steel flux return of the magnet. Charged hadrons are identified by dE/dx measurements in the tracking detectors and in a ring-imaging Cherenkov detector surrounding the drift chamber. The trigger, data acquisition and data-monitoring systems, VME- and network-based, are controlled by custom-designed online software. Details of the layout and performance of the detector components and their associated electronics and software are presented.

The heavy ion cooler-storage-ring project (HIRFL-CSR) at Lanzhou

Abstract: HIRFL-CSR, a new ion Cooler-Storage-Ring (CSR) project, is the post-acceleration system of the Heavy Ion Research Facility in Lanzhou (HIRFL). It consists of a main ring (CSRm) and an experimental ring (CSRe). From the HIRFL cyclotron system the heavy ions will be accumulated, cooled and accelerated in the CSRm, then extracted fast to produce radioactive ion beams (RIB) or highly charged heavy ions. Those secondary beams will be accepted and stored by the CSRe for many internal-target experiments with electron cooling.

Scintillation properties of LaBr3:Ce3+ crystals: fast, efficient and high-energy-resolution scintillators

Abstract: The scintillation properties of LaBr 3 doped with different Ce concentrations, studied by means of optical, X-ray, and γ-ray excitation are presented. Under optical and γ-ray excitation, Ce 3+ emission is observed peaking at 356 and 387 nm. For pure LaBr 3 and LaBr 3 doped with 0.5%, 2%, 4% and 10% Ce 3+ we measured a light yield of 17,000±2000, 61,000±5000, 48,000±5000, 48,000±5000 and 45,000±5000 photons per MeV (ph/MeV) of absorbed γ-ray energy, respectively. The scintillation decay curve of LaBr 3 :Ce 3+ can be described by a single exponential decay function with a decay time of 30±5 ns. It represents over 90% of the total light yield. An energy resolution (FWHM over peak position) for the 662 keV full energy peak of, respectively, 2.9±0.1%, 3.8±0.4%, 3.5±0.4% and 3.9±0.4% was observed for LaBr 3 :0.5%, 2%, 4% and 10% Ce 3+ .

Construction, test and commissioning of the triple-gem tracking detector for compass

Abstract: The Small Area Tracking system of the COMPASS experiment at CERN includes a set of 20 large area, fast position-sensitive Gas Electron Multiplier detectors, designed to reliably operate in the harsh radiation environment of the experiment. We describe in detail the design, choice of materials, assembly procedures and quality controls used to manufacture the devices. The test procedure in the laboratory, the performance in test beams and in the initial commissioning phase in the experiment are presented and discussed.

Lead tungstate scintillation material

Abstract: In this paper we summarize the results of a research programme on lead-tungstate (PWO) crystals performed by the CMS Collaboration at CERN, as well as by other groups who promoted the progress of the PWO scintillation crystal technology. Crystal properties, mass production technology, scintillation mechanism, origin of colouring, defects in crystal and radiation induced phenomena, light yield improvement and results of beam tests are described.

The tracking detector of the KLOE experiment

Abstract: The design and construction of the large Drift Chamber for the KLOE experiment at the Frascati φ-factory, DAΦNE, are described. The relevant aspects of the various elements of the detector are reviewed together with a description of the track reconstruction program and of the calibration procedures. The performance of the detector based on measurements with cosmic rays and with e+e− colliding beams during DAΦNE commissioning is presented.

The KLOE electromagnetic calorimeter

Abstract: The KLOE calorimeter is a fine lead-scintillating fiber sampling calorimeter. We describe in the following the calibration procedures and the calorimeter performances obtained after 3 years of data taking. We get an energy resolution for electromagnetic showers of 5.4%/ E (GeV) and a time resolution of 56 ps/ E (GeV) . We also present a measurement of efficiency for low-energy photons.

Current trends in scintillator detectors and materials

Abstract: The last decade has seen a renaissance in inorganic scintillator development for gamma ray detection. Lead tungstate (PbWO4) has been developed for high energy physics experiments, and possesses exceptionally high density and radiation hardness, albeit with low luminous efficiency. Lutetium orthosilicate or LSO (Lu2SiO5:Ce) possesses a unique combination of high luminous efficiency, high density, and reasonably short decay time, and is now incorporated in commercial positron emission tomography (PET) cameras. There have been advances in understanding the fundamental mechanisms that limit energy resolution, and several recently discovered materials (such as LaBr3:Ce) possess energy resolution that approaches that of direct solid state detectors. Finally, there are indications that a neglected class of scintillator materials that exhibit near band-edge fluorescence could provide scintillators with sub-nanosecond decay times and high luminescent efficiency.

Spectrum unfolding, sensitivity analysis and propagation of uncertainties with the maximum entropy deconvolution code MAXED

Abstract: MAXED was developed to apply the maximum entropy principle to the unfolding of neutron spectrometric measurements. The approach followed in MAXED has several features that make it attractive: it permits inclusion of a priori information in a well-defined and mathematically consistent way, the algorithm used to derive the solution spectrum is not ad hoc (it can be justified on the basis of arguments that originate in information theory), and the solution spectrum is a non-negative function that can be written in closed form. This last feature permits the use of standard methods for the sensitivity analysis and propagation of uncertainties of MAXED solution spectra. We illustrate its use with unfoldings of NE 213 scintillation detector measurements of photon calibration spectra, and of multisphere neutron spectrometer measurements of cosmic-ray induced neutrons at high altitude (∼20 km) in the atmosphere.

Light output and energy resolution of Ce3+-doped scintillators

Abstract: The systematic trends regarding wavelength of emission, maximum obtainable scintillation light output, gamma-ray energy resolution, and scintllation decay time of Ce3+-doped fluorides, chlorides, bromides, iodides, oxides, sulfides, and selenides are reviewed. Theoretical limits will be compared with actually achieved values. The relation between energy resolution and non-proportional response of scintillators will be discussed.

The ANTARES optical module

Abstract: The ANTARES collaboration is building a deep sea neutrino telescope in the Mediterranean Sea. This detector will cover a sensitive area of typically 0.1 km-squared and will be equipped with about 1000 optical modules. Each of these optical modules consists of a large area photomultiplier and its associated electronics housed in a pressure resistant glass sphere. The design of the ANTARES optical module, which is a key element of the detector, has been finalized following extensive R & D studies and is reviewed here in detail.

Intrinsic energy resolution of NaI(Tl)

Abstract: The light output for ∅10 mm×10 mm and ∅75 mm×75 mm NaI(Tl) crystals and energy resolution were measured for γ-ray energies ranging from 16–1333 keV. These measurements enabled the observation of the light yield nonproportionality behavior and allowed the determination of the intrinsic resolution after correcting for the measured resolution for photomultiplier tube (PMT) statistics. The intrinsic resolution was then compared with the nonproportionality component. The latter was calculated using measured electron response, Monte Carlo N Particle code (MCNP4B), and the simplified cascade sequence for NaI(Tl). This comparison allowed the identification of the intrinsic resolution component associated with δ-rays. Consequently, it was shown that the δ-ray component is the most dominant component of the NaI(Tl) intrinsic resolution.

A broad-application microchannel-plate detector system for advanced particle or photon detection tasks: large area imaging, precise multi-hit timing information and high detection rate

Abstract: New applications for single particle and photon detection in many fields require both large area imaging performance and precise time information on each detected particle. Moreover, a very high data acquisition rate is desirable for most applications and eventually the detection and imaging of more than one particle arriving within a microsecond is required. Commercial CCD systems lack the timing information whereas other electronic microchannel plate (MCP) read-out schemes usually suffer from a low acquisition rate and complicated and sometimes costly read-out electronics. We have designed and tested a complete imaging system consisting of an MCP position readout with helical wire delaylines, single-unit amplifier box and PC-controlled time-to-digital converter (TDC) readout. The system is very flexible and can detect and analyse position and timing information at single particle rates beyond 1 MHz. Alternatively, multihit events can be collected and analysed at about 20 kHz rate. We discuss the advantages and applications of this technique and then focus on the detector’s ability to detect and analyse multiple hits. r 2002 Elsevier Science B.V. All rights reserved.

A new lutetia-based ceramic scintillator for X-ray imaging

Abstract: We report a new scintillator based on a transparent ceramic of Lu 2 O 3 :Eu. The material has an extremely high density of 9.4 g/cm 3 , a light output comparable to CsI:Tl, and a narrow band emission at 610 nm that falls close to the maximum of the response curve of CCDs. Pixelation of the scintillator to prevent lateral spread of light enhances the spatial and contrast resolution, providing imaging performance that equals or surpasses all other currently known scintillators. Upon further development of readout technologies to take full advantage of its transparency, the new scintillator should play a major role in digital radiographic systems.

Simulation of non-ionising energy loss and defect formation in silicon

Abstract: Simulation studies of Non-Ionising Energy Loss (NIEL) in silicon exposed to various types of hadron irradiation are presented. A simulation model of migration and clustering of the produced primary defects is developed. Although there are many uncertainties in the input parameters it is shown that the model is consistent with experimental observations on standard and oxygen-enriched silicon. However, the model makes the rather dramatic prediction that NIEL scaling of leakage current and effective doping concentration can be violated significantly even in standard silicon. Although there are possible shortcomings in the model which might account for this, it is shown that at the microscopic level there is, indeed, no obvious reason for an exact NIEL scaling. Furthermore, it is argued that, contrary to common belief, even a significant violation of NIEL scaling can still be consistent with experimental data.

Temperature dependence of the fast, near-band-edge scintillation from CuI, HgI2, PbI2, ZnO:Ga and CdS:In

Abstract: We present temperature-dependent pulsed X-ray data on the decay time spectra, wavelengths, and intensities of fast (ns) radiative recombination in five direct, wide-bandgap semiconductors: CuI, HgI2, PbI2, and n-doped ZnO:Ga and CdS:In. At 12 K the luminosity of powder samples is 0.30, 1.6, 0.40, 2.0, and 0.15, respectively, relative to that of BGO powder at room temperature. Increasing the temperature of CuI to 346 K decreases the luminosity by a factor of 300 while decreasing the fwhm of the decay time spectra from 0.20 to 0.11 ns. Increasing the temperature of HgI2 to 102 K decreases the luminosity by a factor of 53 while decreasing the fwhm from 1.6 to 0.5 ns. Increasing the temperature of PbI2 to 165 K decreases the luminosity by a factor of 27 while decreasing the fwhm from 0.52 to 0.15 ns. Increasing the temperature of ZnO:Ga to 365 K decreases the luminosity by a factor of 33 while decreasing the fwhm from 0.41 to 0.21 ns. Increasing the temperature of CdS:In to 295 K decreases the luminosity by a factor of 30 while decreasing the fwhm from 0.20 to 0.17 ns. All emission wavelengths are near the band edge. The luminosities decrease much faster than the radiative lifetimes, therefore, the reduction in luminosity is not primarily due to thermal quenching of the excited states, but mostly due to thermally activated trapping of charge carriers on nonradiative recombination centers. Since the radiative and nonradiative processes occur on different centers, increasing the ratio of radiative to nonradiative centers could result in a class of inorganic scintillators whose decay time and radiative efficiency would approach fundamental limits (i.e.

Bonner sphere spectrometers—a critical review

Abstract: The basic characteristics of Bonner sphere spectrometry systems are first described, followed by a review of the different types of system which have been built, and of how their response functions have been determined. Spectrum unfolding and recent developments are covered briefly. The practical considerations for users are emphasised wherever possible, and the advantages, disadvantages, and problems of using this spectrometer are discussed.

Positron emission particle tracking using the new Birmingham positron camera

Abstract: Since 1985 a positron camera consisting of a pair of multi-wire proportional chambers has been used at Birmingham for engineering studies involving positron emitting radioactive tracers. The technique of positron emission particle tracking (PEPT), developed at Birmingham, whereby a single tracer particle can be tracked at high speed, has proved particularly powerful. The main limitation of the original positron camera was its low sensitivity and correspondingly low data rate. A new positron camera has recently been installed; it consists of a pair of NaI (Tl) gamma camera heads with fully digital readout and offers an enormous improvement in data rate and data quality. The performance of this camera, and in particular the improved capabilities it brings to the PEPT technique, are summarised.

cMiCE: a high resolution animal PET using continuous LSO with a statistics based positioning scheme

Abstract: Objective : Detector designs for small animal scanners are currently dominated by discrete crystal implementations. However, given the small crystal cross-sections required to obtain very high resolution, discrete designs are typically expensive, have low packing fraction, reduced light collection, and are labor intensive to build. To overcome these limitations we have investigated the feasibility of using a continuous miniature crystal element (cMiCE) detector module for high resolution small animal PET applications. Methods : The detector module consists of a single continuous slab of LSO, 25×25 mm 2 in exposed cross-section and 4 mm thick, coupled directly to a PS-PMT (Hamamatsu R5900-00-C12). The large area surfaces of the crystal were polished and painted with TiO 2 and the short surfaces were left unpolished and painted black. Further, a new statistics based positioning (SBP) algorithm has been implemented to address linearity and edge effect artifacts that are inherent with conventional Anger style positioning schemes. To characterize the light response function (LRF) of the detector, data were collected on a coarse grid using a highly collimated coincidence setup. The LRF was then estimated using cubic spline interpolation. Detector performance has been evaluated for both SBP and Anger based decoding using measured data and Monte Carlo simulations. Results : Using the SBP scheme, edge artifacts were successfully handled. Simulation results show that the useful field of view (UFOV) was extended to ∼22×22 mm 2 with an average point spread function of ∼0.5 mm full width of half maximum (FWHM PSF ). For the same detector with Anger decoding the UFOV of the detector was ∼16×16 mm 2 with an average FWHM PSP of ∼0.9 mm. Experimental results yielded similar differences between FOV and resolution performance. FWHM PSF for the SBP and Anger based method was 1.4 and 2.0 mm, uncorrected for source size, with a 1 mm diameter point source, respectively. Conclusion : A continuous detector module with an average FWHM PSF approaching one millimeter has been built and tested. Furthermore, the results demonstrate that our SBP scheme yields improved performance over traditional Anger techniques for our cMiCE detector.

Measurement of the energy spectrum of cosmic-ray induced neutrons aboard an ER-2 high-altitude airplane.

Abstract: Crews working on present-day jet aircraft are a large occupationally exposed group with a relatively high average effective dose from galactic cosmic radiation. Crews of future high-speed commercial aircraft flying at higher altitudes would be even more exposed. To help reduce the significant uncertainties in calculations of such exposures, the atmospheric ionizing radiation (AIR) project, an international collaboration of 15 laboratories, made simultaneous radiation measurements with 14 instruments on five flights of a NASA ER-2 high-altitude aircraft. The primary AIR instrument was a highly sensitive extended-energy multisphere neutron spectrometer with lead and steel shells placed within the moderators of two of its 14 detectors to enhance response at high energies. Detector responses were calculated for neutrons and charged hadrons at energies up to 100 GeV using MCNPX. Neutron spectra were unfolded from the measured count rates using the new MAXED code. We have measured the cosmic-ray neutron spectrum (thermal to >10 GeV), total neutron fluence rate, and neutron effective dose and dose equivalent rates and their dependence on altitude and geomagnetic cutoff. The measured cosmic-ray neutron spectra have almost no thermal neutrons, a large “evaporation” peak near 1 MeV and a second broad peak near 100 MeV which contributes about 69% of the neutron effective dose. At high altitude, geomagnetic latitude has very little effect on the shape of the spectrum, but it is the dominant variable affecting neutron fluence rate, which was eight times higher at the northernmost measurement location than it was at the southernmost. The shape of the spectrum varied only slightly with altitude from 21 km down to 12 km (56–201 g cm −2 atmospheric depth), but was significantly different on the ground. In all cases, ambient dose equivalent was greater than effective dose for cosmic-ray neutrons.

Pulse shape analysis of liquid scintillators for neutron studies

Abstract: The acquisition of signals from liquid scintillators with Flash ADC of high sampling rate ð 1G S=sÞ has been investigated. The possibility to record the signal waveform is of great advantage in studies with g’s and neutrons in a high count-rate environment, as it allows to easily identify and separate pile-up events. The shapes of pulses produced by g-rays and neutrons have been studied for two different liquid scintillators, NE213 and C6D6: A 1-parameter fitting procedure is proposed, which allows to extract information on the particle type and energy. The performance of this method in terms of energy resolution and n=g discrimination is analyzed, together with the capability to identify and resolve pile-up events. r 2002 Elsevier Science B.V. All rights reserved.

Discharge studies and prevention in the gas electron multiplier (GEM)

Abstract: The gas electron multiplier (GEM) used as single proportional counter or in a cascade of two or more elements, permits to attain high gains and to perform detection and localization of ionizing tracks at very high radiation rates. As in other micro-pattern detectors, however, the occasional occurrence of heavily ionizing trails may trigger a local breakdown, with possible harmful consequences on the device itself and on the readout electronics. This paper describes a systematic investigation of the discharge mechanisms in single and multiple GEM structures, and suggests various strategies to reduce both the energy and the probability of the discharges.

Effective trapping time of electrons and holes in different silicon materials irradiated with neutrons, protons and pions

Abstract: Silicon diodes fabricated on oxygenated and non-oxygenated silicon wafers with different bulk resistivities (1, 2 and 15 kO cm) were irradiated with neutrons, pions and protons to fluences up to 2:4 � 10 14 n=cm � 2 : Effective trapping times for electrons and holes were determined by the charge correction method in the temperature range between � 501C and 201C: The measured effective trapping probabilities scale linearly with fluence and decrease with increasing temperature. Irradiation with charged hadrons resulted in about 30% higher trapping probabilities than with neutrons at the same equivalent fluence. No dependence on silicon resistivity and oxygen concentration was found. The temperature dependence could be parameterized by a power-law scaling. Accelerated annealing at 601C showed a 30% increase of hole trapping, measured at 101C; and a decrease by about the same amount for electron trapping, both at a time scale of 10 h: r 2002 Elsevier Science B.V. All rights reserved. PACS: 85.30.De; 29.40.Wk; 29.40.Gx

Measurement of neutron dose equivalent to proton therapy patients outside of the proton radiation field

Abstract: Measurements of neutron dose equivalent values and neutron spectral fluences close to but outside of the therapeutic proton radiation field are presented. The neutron spectral fluences were determined at five locations with Bonner sphere measurements and established by unfolding techniques. More than 50 additional neutron dose equivalent values were measured with LiI and BF 3 thermal neutron detectors surrounded by a 25 cm polyethylene moderating sphere. For a large-field treatment, typical values of neutron dose equivalent per therapeutic proton absorbed dose, H / D , at 50 cm distance from isocenter, range from 1 mSv/Gy (at 0° with respect to the proton beam axis) to 5 mSv/Gy (at 90°). Experiments reveal that H / D varies significantly with the treatment technique, e.g., patient orientation, proton beam energy, and range-modulation. The relative uncertainty in H / D values is approximately 40% (one standard deviation).

High resolution X-ray detector for synchrotron-based microtomography

Abstract: Synchrotron-based microtomographic devices are powerful, non-destructive, high-resolution research tools. Highly brilliant and coherent X-rays extend the traditional absorption imaging techniques and enable edge-enhanced and phase-sensitive measurements. At the Materials Science Beamline MS of the Swiss Light Source (SLS), the X-ray microtomographic device is now operative. A high performance detector based on a scintillating screen optically coupled to a CCD camera has been developed and tested. Different configurations are available, covering a field of view ranging from 715×715 μm 2 to 7.15×7.15 mm 2 with magnifications from 4× to 40×. With the highest magnification 480 lp/mm had been achieved at 10% modulation transfer function which corresponds to a spatial resolution of 1.04 μm. A low-noise fast-readout CCD camera transfers 2048×2048 pixels within 100–250 ms at a dynamic range of 12–14 bit to the file server. A user-friendly graphical interface gives access to the main parameters needed for running a complete tomographic scan. This novel device will be used to study the physical structure and chemical composition of biological and technical materials, e.g. enabling pseudo-dynamic testing of bone samples to establish structure–function relationships in simulated osteoporosis or enabling non-destructive testing during the development of modern composite materials.

Detection of the primary scintillation light from dense Ar, Kr and Xe with novel photosensitive gaseous detectors

Abstract: The detection of primary scintillation light in combination with the charge or secondary scintillation signals is an efficient technique in determining the events “ t =0” as well as particle/photon separation in large mass TPC detectors filled with noble gases and/or condensed noble gases. The aim of this work is to demonstrate that costly photo-multipliers could be replaced by cheap novel photosensitive gaseous detectors: wire counters, GEMs or glass capillary plates coupled with CsI photocathodes. We have performed systematic measurements with Ar, Kr and Xe gases at pressures in the range of 1–50 atm as well as some preliminary measurements with liquid Xe and liquid Ar. With the gaseous detectors we have succeeded in detecting a scintillation light produced by 22 keV X-rays with an efficiency close to 100%. We also detected the scintillation light produced by β’ s (5 keV deposit energy) with an efficiency close to 25%. Successful detection of scintillation from 22 keV X-rays open new experimental possibilities not only for nTOF and ICARUS experiments, but also in others, such as WIMP's search through nuclear recoil emission.

The origin of double peak electric field distribution in heavily irradiated silicon detectors

Abstract: The first observation of double peak (DP) electric field distribution in heavily neutron irradiated (>10 14 n/cm 2 ) semiconductor detectors has been published about 6 yr ago. However, this effect was not quantitatively analyzed up to now. The explanation of the DP electric field distribution presented in this paper is based on the properties of radiation induced deep levels in silicon, which act as deep traps, and on the distribution of the thermally generated free carrier concentration in the detector bulk. In the frame of this model, the earlier published considerations on the so-called “double junction (DJ) effect” are discussed as well. The comparison of the calculated electric field profiles at different temperatures with the experimental ones allows one to determine a set of deep levels. This set of deep levels, and their charge filling status are essential to the value and the distribution of space charge in the space charge region in the range of 305–240 K, which is actual temperature range for the main experiments at LHC where silicon detectors are used. This set of deep levels includes the levels located close to the midgap and does not contain the defects with the largest introduction rate −( C i – O i ) and ( V – V ).

Neutron and photon spectrometry with liquid scintillation detectors in mixed fields

Abstract: Liquid scintillation detectors of type NE213 or BC501A are well suited and routinely used for spectrometry in mixed n-γ-fields. Neutron- and photon-induced pulse height spectra may be simultaneously recorded making use of the n/γ-discrimination capability based on pulse shape analysis. The light output functions for the detected secondary charged particles, i.e. electrons, positrons, protons and other charged reaction products, and the pulse height resolution function must carefully be determined. This can be done experimentally, in part via an iterative procedure by comparison with calculations. The response functions can then be reliably calculated by Monte Carlo simulations. Photon response functions calculated with the PHRESP code, which was developed on the basis of the EGS4+PRESTA program package, are in very good agreement with calibrations up to 17 MeV, both in shape and absolute scale. Similarly, neutron response functions calculated with the NRESP7 code well describe the pulse height spectra for monoenergetic neutrons up to 20 MeV, although with some limitations for neutron energies beyond 10 MeV. In the case of measurements in mixed fields, the photon pulse height spectrum has to be corrected for neutron-induced photons generated in the detector assembly. The corresponding response functions may be determined numerically (with the MCNP and the PHRESP codes) or experimentally. Hence, the response matrices necessary for the deconvolution of measured pulse height spectra by the various unfolding procedures included in the HEPRO package are finally calculated with at least six functions per FWHM of the corresponding pulse height resolution. With appropriate counting statistics of the measured pulse height spectra, excellent energy resolution is achieved, e.g. about 20% of the pulse height resolution at the corresponding Compton or recoil proton edge. However, these specifications require that the entire detector system, i.e. scintillator, photomultiplier and associated electronics, exhibits a gain stable over time and independent of count rate and temperature.

Strain imaging by Bragg edge neutron transmission

Abstract: The Bragg edges appearing in the transmitted time-of-flight spectra of polycrystalline materials have been recorded using a two-dimensional array of detectors. Subsequent analysis has enabled maps of the elastic strain to be produced.

NEMUS—the PTB Neutron Multisphere Spectrometer: Bonner spheres and more

Abstract: The original Bonner sphere spectrometer as it is used and characterized by PTB consists of 12 polyethylene spheres with diameters from 7.62 cm (3″) to 45.72 cm (18″) and a 3 He-filled spherical proportional counter used as a central thermal-neutron-sensitive detector and as a bare or cadmium-shielded bare detector. In this paper, a set of four new spheres made of polyethylene with copper or lead inlets is introduced. All spheres are less than 18 kg in mass and their responses to high energy neutrons increase with energy as a result of the increasing ( n , xn ) cross-sections of copper and lead. The fluence response matrix was calculated up to 10 GeV using an extended neutron cross-section library (LA150) and the MCNP(X) Monte Carlo code. Calibration measurements with neutron energies up to 60 MeV were used to compare the calculated response functions to measured values. For measurements outside the laboratory, a miniaturized, battery-powered electronic set-up was developed. This system with the additional, modified spheres is now called NEMUS —Neutron Multisphere Spectrometer.