G. Manessi - Academia.edu (original) (raw)

Papers by G. Manessi

Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014

The well-known foil activation technique was used to calibrate an ionisation chamber employed for... more The well-known foil activation technique was used to calibrate an ionisation chamber employed for the on-line beam monitoring of a 120 GeV c À 1 mixed proton/pion beam at CERN. Two monitoring reactions were employed: the standard 27 Al(p,3pn) 24 Na and the alternative nat Cu(p,x) 24 Na. The parameters on which the technique critically depends and the adopted solutions are thoroughly analysed are the cross-section, the contribution of the competing reactions to the induced activity and the recoil nuclei effect. The experimental results are compared with FLUKA Monte Carlo simulations and with past results obtained with various calibration techniques. The comparison confirms that both reactions can be effectively employed. The nat Cu(p,x) 24 Na reaction shows advantages because its cross-section is known at very high energies with a low uncertainty and the production of 24 Na is not affected by competing low energy neutron-induced reactions. The contribution of the competing reactions in the case of the 27 Al(p,3pn) 24 Na reaction has been estimated to be 4.3%/100 mg cm À 2 , whereas the effect of recoil nuclei is negligible.

Radiation Protection Dosimetry, 2015

The use of conventional Bonner Sphere Spectrometers (BSS) in pulsed neutron fields (PNF) is limit... more The use of conventional Bonner Sphere Spectrometers (BSS) in pulsed neutron fields (PNF) is limited by the fact that proportional counters, usually employed as the thermal neutron detectors, suffer from dead time losses and show severe underestimation of the neutron interaction rate, which leads to strong distortion of the calculated spectrum. In order to avoid these limitations, an innovative BSS, called BSS-LUPIN, has been developed for measuring in PNF. This paper describes the physical characteristics of the device and its working principle, together with the results of Monte Carlo simulations of its response matrix. The BSS-LUPIN has been tested in the stray neutron field at the CERN Proton Synchrotron, by comparing the spectra obtained with the new device, the conventional CERN BSS and via Monte Carlo simulations.

Review of Scientific Instruments, 2014

LUPIN-II is an upgraded version of LUPIN, a novel rem counter first developed in 2010 specificall... more LUPIN-II is an upgraded version of LUPIN, a novel rem counter first developed in 2010 specifically conceived to work in pulsed neutron fields (PNFs). The new version introduces some modifications that improve the performance of the detector, in particular extending its upper detection limit in PNFs. This paper discusses the characteristics and the performance of the instrument. Measurements have been carried out in radiation fields characterized by very different conditions: the detector has first been exposed in PNFs with intensity up to 5 μSv per burst, where it could keep the H*(10) underestimation below 20% up to 500 nSv per burst. It has then been tested in operational conditions around particle accelerators, where it has shown performances similar to that of ionization chambers. Its proper functioning has also been verified in high energy mixed fields, where the experimental results matched the Monte Carlo predictions. Its neutron/photon discrimination capability has been tested in a steady-state photon field where, via an innovative technique based on a threshold set on the derivative of the current signal, it was capable of rejecting a photon H*(10) rate of about 25 mSv/h, and in a mixed neutron/photon field, where a time-based discrimination method was employed.

Progress in Nuclear Science and Technology, 2014

It is well-known that neutron detectors generally suffer from dead-time effects and have strong l... more It is well-known that neutron detectors generally suffer from dead-time effects and have strong limitations when measuring in pulsed radiation fields. An active neutron monitor based on a BF 3 proportional counter and logarithmic electronics was developed to withstand pulsed fields with high intensity, very short duration and high repetition rate. This paper discusses results of preliminary measurements carried out at the Italian National Hadrontherapy Center (CNAO) in Pavia and at the San Raffaele Hospital in Milan. In the first case neutrons were produced by 7 MeV protons accelerated by a LINAC and impinging on a copper Faraday cup. In the second case an electron radiotherapy LINAC produced energy-tunable bremsstrahlung x-rays beams up to 18 MV with an associated neutron component. The neutron monitor was capable to withstand neutron reaction rates up to 2·10 6 s -1 without showing saturation effects. A promising technique is also shown to reject very intense, pulsed gamma fields, due to the innovative operating principle of the detector.

The Long interval, Ultra-wide dynamic Pile-up free Neutron rem counter (LUPIN) is a novel detecto... more The Long interval, Ultra-wide dynamic Pile-up free Neutron rem counter (LUPIN) is a novel detector initially developed for radiation protection purposes, specifically conceived for applications in pulsed neutron fields. The detector has a measurement capability varying over many orders of neutron burst intensity, from a single neutron up to thousands of interactions for each burst, without showing any saturation effect. Whilst LUPIN has been developed for applications in the radiation protection fields, its unique properties make it also well suited to support other beam instrumentation. In this contribution, the design of LUPIN is presented in detail and results from measurements carried out in different facilities summarize its main characteristics. Its potential use as beam loss monitor (BLM) and complementary detector for non-invasive beam monitoring purposes (e.g. to complement a monitor based on proton beam "halo" detection) in medical accelerators is then examined. ...

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2013

Neutron detection Pulsed field Linac Proportional counter Logarithmic amplifier a b s t r a c t A... more Neutron detection Pulsed field Linac Proportional counter Logarithmic amplifier a b s t r a c t A number of studies focused in the last decades on the development of survey meters to be used in pulsed radiation fields. This is a topic attracting widespread interest for applications such as radiation protection and beam diagnostics in accelerators. This paper describes a new instrument specifically conceived for applications in pulsed neutron fields (PNF). The detector, called LUPIN, is a rem counter type instrument consisting of a 3 He proportional counter placed inside a spherical moderator. It works in current mode with a front-end electronics consisting of a current-voltage logarithmic amplifier, whose output signal is acquired with an ADC and processed on a PC. This alternative signal processing allows the instrument to be used in PNF without being affected by saturation effects. Moreover, it has a measurement capability ranging over many orders of burst intensity. Despite the fact that it works in current mode, it can measure a single neutron interaction. The LUPIN was first calibrated in CERN's calibration laboratory with a PuBe source. Measurements were carried out under various experimental conditions at the Helmholtz-Zentrum in Berlin, in the stray field at various locations of the CERN Proton Synchrotron complex and around a radiotherapy linear accelerator at the S. Raffaele hospital in Milan. The detector can withstand single bursts with values of Hn(10) up to 16 nSv/burst without showing any saturation effect. It efficiently works in pulsed stray fields, where a conventional rem-counter underestimates by a factor of 2. It is also able to reject the very intense and pulsed photon contribution that often accompanies the neutron field with good reliability.

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2014

In the framework of the EURADOS working group 11, an intercomparison of active neutron survey met... more In the framework of the EURADOS working group 11, an intercomparison of active neutron survey meters was performed in a pulsed neutron field (PNF). The aim of the exercise was to evaluate the performances of various neutron instruments, including commercially available rem-counters, personal dosemeters and instrument prototypes. The measurements took place at the cyclotron of the Helmholtz-Zentrum Berlin für Materialien und Energie GmbH. The cyclotron is routinely used for proton therapy of ocular tumours, but an experimental area is also available. For the therapy the machine accelerates protons to 68 MeV. The interaction of the proton beam with a thick tungsten target produces a neutron field with energy up to about 60 MeV. One interesting feature of the cyclotron is that the beam can be delivered in bursts, with the possibility to modify in a simple and flexible way the burst length and the ion current. Through this possibility one can obtain radiation bursts of variable duration and intensity. All instruments were placed in a reference position and irradiated with neutrons delivered in bursts of different intensity. The analysis of the instrument response as a function of the burst charge (the total electric charge of the protons in the burst shot onto the tungsten target) permitted to assess for each device the dose underestimation due to the time structure of the radiation field. The personal neutron dosemeters were exposed on a standard PMMA slab phantom and the response linearity was evaluated.

Radiation Protection Dosimetry, 2013

This paper discusses an intercomparison campaign carried out in several locations around the CERN... more This paper discusses an intercomparison campaign carried out in several locations around the CERN Proton Synchrotron. The locations were selected in order to perform the measurements in different stray field conditions. Various neutron detectors were employed: ionisation chambers, conventional and extended range rem counters, both commercial and prototype ones, including a novel instrument called LUPIN, specifically conceived to work in pulsed fields. The attention was focused on the potential differences in the instrument readings due to dead-time losses that are expected to affect most commercial units. The results show that the ionisation chambers and LUPIN agree well with the expected H*(10) values, as derived from FLUKA simulations, showing no relevant underestimations even in strongly pulsed fields. On the contrary, the dead-time losses of the other rem counters induced an underestimation in pulsed fields that was more important for instruments characterised by a higher dead time.

Physical Review C, 2014

Spallation cross sections from thin natural copper and iron targets bombarded by a mixed 120 GeV/... more Spallation cross sections from thin natural copper and iron targets bombarded by a mixed 120 GeV/c proton/pion beam were measured in an activation experiment at CERN. The beam intensity was monitored by a calibrated ionization chamber and the activity of several spallation products was measured (14 for copper and 16 for iron) by γ spectrometry, allowing the absolute cross section of the mixed hadron beam to be derived. Monte Carlo simulations with the FLUKA code provided the ratio between the proton-and pion-induced reaction cross sections for a given spallation product, allowing us to extrapolate the individual cross sections for the protonand the pion-induced reactions. Where possible the values were compared with literature data and showed to be generally in agreement with the highest energy data available.

The present document discusses the results of the measurements carried out during the test run pe... more The present document discusses the results of the measurements carried out during the test run performed before the main beam time of the HRMT-15 (RPINST) experiment in the HiRadMat facility, which is planned for October 2012. A prototype detector, specifically designed for measuring pulsed neutron fields, was employed in different positions in order to evaluate the stray neutron field conditions in the TA7 tunnel of HiRadMat. Critical points to be taken into account for the main experiment in October are presented, along with solutions to overcome them.