A high-resolution large-area detector for quality assurance in radiotherapy.

Hadron therapy is an advanced radiation modality for treating cancer, which currently uses protons and carbon ions. Hadrons allow for a highly conformal dose distribution to the tumour, minimising the detrimental side-effects due to radiation received by healthy tissues. Treatment with hadrons requires sub-millimetre spatial resolution and high dosimetric accuracy.

Comparison between CLYC-6 and 3He for thermal neutron detection.

A Cs2LiYCl6:Ce crystal, enriched in 6Li to > 95% (CLYC-6), was investigated for thermal neutron detection: it was characterised in terms of intrinsic efficiency and γ-ray discrimination capability and compared with a 3He counter (partial 3He pressure 2.3 atm). The intrinsic efficiency was determined by irradiating the detectors with thermal neutrons.

EURADOS REM-COUNTER INTERCOMPARISON AT MAASTRO PROTON THERAPY CENTRE: COMPARISON WITH LITERATURE DATA.

The Maastro Proton Therapy Centre is the first European facility housing the Mevion S250i Hyperscan synchrocyclotron. The proximity of the accelerator to the patient, the presence of an active pencil beam delivery system downstream of a passive energy degrader and the pulsed structure of the beam make the Mevion stray neutron field unique amongst proton therapy facilities. This paper reviews the results of a rem-counter intercomparison experiment promoted by the European Radiation Dosimetry Group at Maastro and compares them with those at other proton therapy facilities.

Joint EURADOS WG9-WG11 rem-counter intercomparison in a Mevion S250i proton therapy facility with Hyperscan pulsed synchrocyclotron.

Objective Proton therapy is gaining popularity because of the improved dose delivery over conventional radiation therapy. The secondary dose to healthy tissues is dominated by secondary neutrons. Commercial rem-counters are valuable instruments for the on-line assessment of neutron ambient dose equivalent (H*(10)).

A thermal neutron source for the CERN radiation Calibration Laboratory.

This work presents the design, construction and experimental characterisation of a lightweight and low-cost thermal neutron assembly, to be used with the existing Am-Be source irradiator of CERN radiation Calibration Laboratory (Cal Lab). The assembly consists of a cylindrical moderator (18 cm diameter, 25.5 cm height and 5.

EURADOS STRATEGIC RESEARCH AGENDA 2020: VISION FOR THE DOSIMETRY OF IONISING RADIATION.

Since 2012, the European Radiation Dosimetry Group (EURADOS) has developed its Strategic Research Agenda (SRA), which contributes to the identification of future research needs in radiation dosimetry in Europe. Continued scientific developments in this field necessitate regular updates and, consequently, this paper summarises the latest revision of the SRA, with input regarding the state of the art and vision for the future contributed by EURADOS Working Groups and through a stakeholder workshop. Five visions define key issues in dosimetry research that are considered important over at least the next decade.

A GEMPix-based integrated system for measurements of 3D dose distributions in water for carbon ion scanning beam radiotherapy.

Purpose: Commercially available systems for ion beam reference dosimetry in water are mainly based on ionization chambers. In those systems, a large number of small detectors are typically arranged in a two-dimensional (2D) array or matrix to achieve high spatial resolution (order of several millimeters) and large field coverage at the same time. The goal of this work was to investigate the reliability of a detector of superior spatial resolution to perform three-dimensional (3D) ionization measurements in carbon ion pencil beams.

Impact of the newly proposed ICRU/ICRP quantities on neutron calibration fields and extended range neutron rem-counters.

In July 2017, the International Commission on Radiation Units and Measurements (ICRU) and the International Commission on Radiological Protection (ICRP) proposed the introduction of new operational quantities for external radiation exposure, with the aim of improving coherence between protection quantities and operational quantities within the system of radiological protection. A change in operational quantities will impact both instrumentation and reference radiation fields used for their calibration. This paper evaluates the potential impact of the new quantity ambient dose, H*, meant to replace ambient dose equivalent, H*(10), on two neutron reference fields, the Am-Be source and the CERF high-energy workplace field, and on the response of two models of extended-range neutron rem counters (LINUS and LUPIN).

CERN IRRADIATION FACILITIES.

CERN provides unique irradiation facilities for applications in dosimetry, metrology, intercomparison of radiation protection devices, benchmark of Monte Carlo codes and radiation damage studies to electronics.

CHARACTERIZATION OF CLYC SCINTILLATOR COUPLED WITH PHOTOMULTIPLIERS AND A LARGE SIPM ARRAY.

CERN Radiation Protection group has recently developed a novel radiation survey meter called B-RAD able to operate in the presence of a strong magnetic field. The B-RAD will be equipped with a series of probes for gamma dose rate, gamma spectrometry and surface contamination measurements. The feasibility of developing a probe for neutron dose rate and possibly spectral measurements is being investigated.

SECONDARY NEUTRON DOSES IN A PROTON THERAPY CENTRE.

The formation of secondary high-energy neutrons in proton therapy can be a concern for radiation protection of staff. In this joint intercomparative study (CERN, SCK•CEN and IBA/IRISIB/ULB), secondary neutron doses were assessed with different detectors in several positions in the Proton Therapy Centre, Essen (Germany). The ambient dose equivalent H(*)(10) was assessed with Berthold LB 6411, WENDI-2, tissue-equivalent proportional counter (TEPC) and Bonner spheres (BS).

A Bonner Sphere Spectrometer for pulsed fields.

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.

Leaching of radionuclides from activated soil into groundwater.

Soil samples collected from the CERN site were irradiated by secondary radiation from the 400 GeV/c SPS proton beam at the H4IRRAD test area. Water samples were also irradiated at the same time. Detailed gamma spectrometry measurements and water scintillation analysis were performed to measure the radioactivity induced in the samples.

A new version of the LUPIN detector: improvements and latest experimental verification.

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.

New radiation protection calibration facility at CERN.

The CERN radiation protection group has designed a new state-of-the-art calibration laboratory to replace the present facility, which is >20 y old. The new laboratory, presently under construction, will be equipped with neutron and gamma sources, as well as an X-ray generator and a beta irradiator. The present work describes the project to design the facility, including the facility placement criteria, the 'point-zero' measurements and the shielding study performed via FLUKA Monte Carlo simulations.

Instrument intercomparison in the high-energy mixed field at the CERN-EU reference field (CERF) facility.

This paper discusses an intercomparison campaign performed in the mixed radiation field at the CERN-EU (CERF) reference field facility. Various instruments were employed: conventional and extended-range rem counters including a novel instrument called LUPIN, a bubble detector using an active counting system (ABC 1260) and two tissue-equivalent proportional counters (TEPCs). The results show that the extended range instruments agree well within their uncertainties and within 1σ with the H*(10) FLUKA value.

High-energy quasi-monoenergetic neutron fields: existing facilities and future needs.

The argument that well-characterised quasi-monoenergetic neutron (QMN) sources reaching into the energy domain >20 MeV are needed is presented. A brief overview of the existing facilities is given, and a list of key factors that an ideal QMN source for dosimetry and spectrometry should offer is presented. The authors conclude that all of the six QMN facilities currently in existence worldwide operate in sub-optimal conditions for dosimetry.

Comparison of the performance of different instruments in the stray neutron field around the CERN Proton Synchrotron.

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.

Applications of particle accelerators in medicine.

There are nearly 20,000 particle accelerators in operation worldwide, about half of them employed for biomedical uses. This paper focuses on some recent advances in the two main medical domains where accelerators find their use, radionuclide production and radiation therapy. The paper first discusses the use of high-energy electron and proton accelerators for the potential, future production of (99)Mo, which is presently provided by fission reactors.

Shielding of proton accelerators.

This paper discusses some of the methods that can be employed for calculating shielding of proton accelerators, showing that a simple analytical model is often useful for a first estimate before going into complex Monte Carlo simulations. In particular what we call the Monte Carlo 'hybrid' approach, which employs source terms and attenuation length data calculated by Monte Carlo simulations under generic geometrical conditions, with a point-source line-of-sight model is discussed. Examples are given of the application of this method to the shielding calculations of two versions of the CERN SPL (2- and 3.

Instrument response in complex radiation fields.

This paper aims at giving an overview of the main issues for estimating the radiation protection quantities in complex radiation fields. The measurability (or non-measurability) of the radiation protection quantities is discussed together with the main approaches for their estimate. The main mechanisms through which the various components of complex radiation fields are generated are also outlined.

Further progress in the characterisation of complex radiation fields.

One of the topics which forms part of CONRAD project addresses the problems related to the dosimetry of complex-mixed radiation fields at workplaces. This topic was included in work package (WP) 6. WP 6 was established to co-ordinate research activities in two areas:the development of new techniques and the improvement of current techniques for characterisation of complex workplace fields (including high-energy fields and pulsed fields): measurement and calculation of particle energy and direction distributions (Subgroup A); and model improvements for dose assessment of solar particle events (Subgroup B).

Workplace characterisation in mixed neutron-gamma fields, specific requirements and available methods at high-energy accelerators.

A good knowledge of the radiation field present outside the shielding of high-energy particle accelerators is very important to be able to select the type of detectors (active and/or passive) to be employed for area monitoring and the type of personal dosemeter required for estimating the doses received by individuals. Around high-energy electron and proton accelerators the radiation field is usually dominated by neutrons and photons, with minor contributions from other charged particles. Under certain circumstances, muon radiation in the forward beam direction may also be present.

Sensitivity study of CR39 track detector in an extended range Bonner sphere spectrometer.

Bonner sphere spectrometers (BSS) are being used widely in neutron spectrometry since 1960. The response to neutrons of these moderating detectors spans over a broad energy range. This work discusses the measurement of the sensitivity of an extended range BSS hosting a CR39 nuclear track detector coupled to a boron converter.

The problems associated with the monitoring of complex workplace radiation fields at European high-energy accelerators and thermonuclear fusion facilities.

The European Commission is funding within its Sixth Framework Programme a three-year project (2005-2007) called CONRAD, COordinated Network for RAdiation Dosimetry. The organisational framework for this project is provided by the European Radiation Dosimetry Group EURADOS. One task within the CONRAD project, Work Package 6 (WP6), was to provide a report outlining research needs and research activities within Europe to develop new and improved methods and techniques for the characterisation of complex radiation fields at workplaces around high-energy accelerators, but also at the next generation of thermonuclear fusion facilities.