CNAO

Pavia, Italy

General information

The ARDENT collaboration submitted an application for beam time via ULICE in February 2013.

A description of the proposed experiments can be found here:

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Six shifts of 8 hours at CNAO were allocated to ARDENT in the period from February to June 2014.

A list of publications written with results from the ULICE campaigns (at CNAO and HIT) can be found here:

List of publications



The results of the measurements performed with GEM and GEMPIX were presented at CNAO in February 2015, followed by discussions of future applications for beam monitoring, dosimetric measurements and quality assurance.

You can download the presentation here:

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First experiment

Date: 1 February 2014

Experiment leader: Marco Silari (CERN) and Marco Caresana (PoliMi)

Participants: S. George, M. Magistris, G. Manessi, F. Murtas, M. Silari (CERN), and M. Caresana, C. Cassel (PoliMi)

Description:

One stack of CR-39 dosimeters were irradiated with a proton beam, behind 32 mm of water-equivalent phantom. The beam intensity was around 105 particles (total irradiation). The same setup was repeated with a broad beam in order to further reduce the beam intensity seen by the dosimeters, down to 103 particles.

Several sets of CR-39 dosimeters were placed at different angles from the beam line in order measure secondary neutrons. The Lupin detector was placed in a symmetric position at 45 degrees. These measurements will be compared with data taken in a previous measurement under the same conditions with the detector Wendi II.

Measurements with the GEMPIX were performed without the high-voltage gas amplification. The aim of these measurements was to investigate if high intensity particle beam caused a timepix ASIC without any sensor to count. A similar effect was also observed at a low-energy proton cyclotron in Berne (CH), and is probably due to Single Event Upsets. From this first experiment at CNAO it was concluded that fluxes of thousands of protons per pixel caused a definite effect in the ASIC, which was linearly correlated with the beam intensity. The measured spatial and time signal in the ASIC was in good agreement with the expected profile of the beam.

Second experiment

Date: 8 March 2014 (13:00 - 21:00 pm)

Experiments leaders: Marco Caresana (PoliMi) , Alberto Fazzi (PoliMi) and Fabrizio Murtas(CERN)

Participants: M. Caresana, C. Cassel, A. Fazzi, E. Sagia and A. Sashala Naik (PoliMi); E. Azi, S. George, F. Murtas, S. Puddu (CERN)

Description

The first part of the experiment was dedicated to in-beam measurements with GEMPIX, GEM and CR-39 dosimeters. Measurements of 2D image of the beam were carried out with the highly pixelated GEMPIX detector (3×3 cm2 active area) and with the standard GEM detector (3×3 cm2 active area with 2×2 mm2 pads). A high-voltage scan (108 particles per spill) and an intensity scan (from 106 to 108 particles per spill) were performed with protons at 200 MeV and with ions at 400 MeV per nucleon.

A set of measurements were performed in the Bragg peak region of the hadron beam with a stack of CR-39 dosimeters, for both a proton and a carbon beam. These measurements aimed at the assessment of the beam dimension (longitudinal and transversal straggling), LET distribution on each track detector, fragmentation and mapping of the neutron field around the target. More information can be found here:

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The last part of the experiment focused on in-phantom measurements with Si-microdosimeter. Microdosimetric measurements were performed in a water phantom irradiated with 400 MeV per nucleon carbon ions. Only the single stage silicon telescope microdosimeters were used. These measurements allowed setting up the beam, the detector and instrumentation parameters in such a way as to minimize pulse pile up and optimize the electronic signal processing. Measurements were performed at a few different locations inside the phantom in the distal zone, with low beam intensity (about 105 particles per spill).

Third experiment

Date: 5 April 2014 (16:00 - 24:00 pm)

Experiments leaders: S. Agosteo, A. Pola (PoliMi), P. Colautti, V. Conte (LNL)

Participants: S. Agosteo, D. Bortot, M.V. Introini, A. Pola, E. Sagia and A. Sashala Naik (PoliMi); P. Colautti, V. Conte, D. Moro, S. Chiriotti Alvarez (LNL).

Description:

The experiment aimed at measuring microdosimetric spectra across a spread-out Bragg peak (SOBP) of carbon ions. A clinical SOBP, uniform in biological dose, was delivered over a 30×30×30 mm3 cube. The maximum energy per nucleon of the carbon ion beam was 362 MeV.

A pixellated silicon-telescope microdosimeter was used in the first part of the experiment. This detector is constituted by a matrix of cylindrical ΔE elements (about 2 μm in thickness) and a single residual-energy E stage (500 μm thick). The nominal diameter of the ΔE elements is about 9 um and the width of the pitch separating the elements is about 41 um. More than 7000 pixels are connected in parallel to give an effective sensitive area of about 0.5 mm2. The ion beam intensity was of the order of 106 particles per spill for minimizing the rate of pulse pile-up. Measurements were performed at three different depths across the SOBP: proximal, central and distal.

A mini-TEPC (tissue-equivalent proportional counter) was used in the second part of the experiment. The external diameter of the mini-TEPC is 2.7 mm, the same as that of a 8 french (i.e. 2.7 mm) cannula which is employed for mini-invasive surgery. Its sensitive volume is cylindrical (diameter and height 0.9 mm). The anode is a wire of gold-plated tungsten, 10 um in diameter, and the cathode is made of A-150 plastic, 0.35 mm in thickness. The mini-TEPC is inserted in a titanium probe 2.7 mm in diameter, 170 mm in length, electrically grounded. The insulation between the conductive A-150 cathode and the titanium probe is ensured by a 0.35 mm thick Rexolite cylinder. The propane-based tissue-equivalent gas flows continuously through the sensitive volume in order to avoid aging effects that can give rise to gas gain shifts. Measurements were performed across the SOBP at the same depths where the silicon detector was placed in the first part of the experiment. Further depths were investigated. The ion beam intensity was ~ 5 107 ions per spill. Microdosimetric spectra were collected at 5 depths in a water phantom, namely at 201, 213,6, 213,6. 228,6 and 230 mm. In spite of the relatively high noise (the threshold has been set at ~ 20 keV/um) the crosser peak was well visible, as well as the carbon edge at 230 mm of depth. The carbon edge-value for soft tissue was used to calibrate all the spectra.

Two stacks of CR-39 detectors were irradiated in the third part of the experiment with a mono-energetic beam of 400 MeV per nucleon carbon ions.

Fourth experiment

Date: 3 May 2014 (06:00 - 14:00 pm)

Experiment leaders: Fabrizio Murtas and Marco Silari (CERN)

Participants: E. Aza, S. George, F. Murtas, S. Puddu, M. Silari (CERN)

Description

This experiment was performed with a carbon beam with intensity from 1×106 to 5×108 particles per treatment and energy of 279 MeV/u, which corresponds to a penetration of about 15 cm in water.

A water phantom with dimensions 49×39×50 cm3 was employed for the measurements. A head-on triple GEM detector was placed in various positions around the water phantom in order to measure the scattered fast neutrons. The detector was also placed in front of the beam and a 10×10 cm2 X-Y spot scan was performed. The intensity of the beam was 1×106 particles per spot.

A GEMPix (a new detector consisting of a triple GEM coupled to a quad Timepix asic for readout) was used to scan the energy deposited at 23 different depths in the phantom. The detector was also used to count the number of primary beam particles at six different depths, and to record the dE/dx of individual components of the beam behind the Bragg peak.

A 2×2 cm2 X-Y spot scan was performed with beam intensity of 5×106 particles per spot. A preliminary test of a Timepix with a novel multilayer neutron converter was performed, approximately 50 cm from the phantom in order to determine the detector response to fast neutrons.

Fifth experiment

Date: 8 June 2014 (14h00 - 22h00)

Experiment leaders: M. Caresana, A. Fazzi (Polimi), and S. Rollet (AIT)

Participants:

Andrea Pola, Eleni Sagia, Alberto Fazzi, Christopher Cassell, Marco Caresana, Davide Moro, Sabriana Chiriotti Alvarez, Alvin Sashala Naik (Polimi and INFN Legnaro); Sofia Rollet and Andrej Sipaj (AIT).

Description:

The first part of the experiment at CNAO was designed to test 3 different adhesives and 2 different connection techniques in order to evaluate the best suitable connecting material for a thorax phantom construction. Film measurements were done inside a polystyrene phantom where a first block was composed of two glued polystyrene blocks. These blocks were placed in the beam axis with the glue stripe oriented parallel to the beam. The dose was delivered by a proton scanning beam (3×3 cm2) with SOBP with centre at 21 cm water-equivalent depth (169.7-185.6 MeV) and measured with 3 films (GAFCHROMIC EBT) placed inside the polystyrene phantom. In addition, two films per experiment were placed parallel and perpendicular to the beam. Out of the 3 tested adhesives, the Pattex 100% Multi-Power Kleber showed the lowest effect on beam spread and attenuation when used as a phantom connection material.

A stack of CR-39 track detectors from MI.AM srl was also placed within the experimental setup. Previous experiments at CNAO using carbon ions proved to be conclusive for the study of the track parameters used to calculate absorbed dose and dose equivalent. In this experiment, the tracks created in the detectors by the proton beam will be used to study the dependence of the measured linear energy transfer (LET) of protons on the track parameters. In particular, there seems to be a non-linear response in terms of tracks’ sizes around the CR-39 detection threshold of 10 keV/µm, This effect and its impact on the measured dose are still to be investigated. Furthermore, the absorbed dose measured with the two types of passive detectors (CR-39 and GAFCHROMIC EBT) will be evaluated by the research teams in POLIMI and AIT, and compared to results from the Monte Carlo Particle Transport codes MCNPX and FLUKA.

The second part of the experiment was dedicated to microdosimetry and aimed at completing the experiment of the April 5th 2014. Microdosimetric measurements were performed across the clinical Spread-Out-Bragg-Peak (30×30×30 mm3) in a water phantom irradiated with 400 MeV/u carbon ions. A Tissue-Equivalent Proportional Counter with a millimetric sensitive zone (mini-TEPC) and a segmented silicon telescope were used for this purpose. Measurements were performed at two different depths inside the phantom (inside the SOBP and distal to the SOBP), with beam intensities in the range from 5×105 to 5×106 particles per spill on 1 cm2 spot.

Sixth experiment

Date: 5-6 July 2014 (14:00 - 22:00 and 07:00 - 13:00)

Experiment Leaders: F. Murtas

Participants: E. Aza, S. George, F. Murtas, S. Puddu

Description

This experiment was performed with carbon and proton beams, with intensity from 106 to 5×108 particles per treatment (carbon) and from 108 to 2×109 (proton). The energy of the beam was set to reach a depth of 125 mm in H2O (i.e. 252 MeV/u for carbon and 132.95 MeV for proton). An automatized water phantom with dimensions 49×39×50 cm3 was used. One of the possible beam delivery modalities with hadron beams consists in the scan of the cancer region with the beam in X and Y directions. In order to deliver a uniform dose across the treated volume this must be uniformly irradiated. Two head-on triple GEM detectors, filled with Ar-CO2 gas mixture (70%-30%), were placed in front of the beam in order to measure the beam profile and assess its spatial uniformity. In particular, an X-Y spot scan was performed over areas of 2×2 cm2 and 4×4 cm2, with different beam intensities. A radiochromic foil was placed in front of the GEM for comparison, and the data acquisition was synchronised with the GEMPix measuring inside the water phantom. A GEMPix filled with Ar-CO2-CF4 (45%-15%-40%) gas mixture was placed inside the water phantom within an appropriated plexiglass box. The GEMPix was used to scan the energy deposition of carbon and proton beams at different depths in the phantom and to record the position of the Bragg peak.

HIMAC

Chiba, Japan

General description

The experimental campaign was performed by Centre for Medical Radiation Physics of the University of Wollongong, in cooperation with the Politecnico of Milano and aimed at acquiring microdosimetric spectra with various silicon detectors, directly comparing them and verifying their conformity. The irradiations were carried out with pristine and SOBP carbon ion beams of 290 MeV per nucleon.

Australia is considering the development of a Heavy Ion Therapy (HIT) facility for treatment and research, an initiative that was led by the Australian Science and Technology Organization (ANSTO). The Centre for Medical Radiation Physics (CMRP), in collaboration with ANSTO, has been very active in Hadron Therapy research for many years. Part of this research program was established in 2012 in collaboration with the National Institute for Radiological Science (NIRS), in Japan.

The University of Wollongong has recently signed a MOU with NIRS for research collaboration on HIT. This research also covers the evaluation of RBE of heavy ion beams and the development of new fast methods for Quality Assurance of RBE, as well as physical dose distribution in C-12 therapy. The beam time granted for these experiments at HIMAC is the result of successful applications by Prof Anatoly Rozenfeld (CMRP), which led to new opportunities to extend a joint CMRP- Polimi experimental research at NIRS, HIMAC.

First experiment

Date: 25 - 26 July 2013

Experiment Leader: A. Rozenfeld (CMRP - UOW), S. Agosteo (PoliMi)

Participants: D. Prokopovich (ANSTO), L.T. Tran (CMRP - UOW), A. Fazzi (PoliMi), E. Sagia (PoliMi)

Description:

During the first part of the experiment, dE-E stage detectors of both kinds (M1 prototype and pixelated silicon-telescope microdosimeters) were placed at different depths of a PMMA phantom and were irradiated in order to acquire the microdosimetric spectra.

During the second part, microdosimeters of the type CMRP SOI (Silicon on Insulator, 1st and 2nd generation) were placed in the PMMA phantom and simultaneously measured along and downstream of the Bragg Peak (BP) and Spread Out Bragg Peak (SOBP). The purpose of the experiment was to derive the RBE from microdosimetric measurements and compare it with results from the Tissue Equivalent Proportional Counter (TEPC).

Second experiment

Date: 12 April 2014

Experiment Leader: A. Rozenfeld (CMRP - UOW), S. Agosteo (PoliMi)

Participants: M. Petasecca(CMRP - UOW), M. Newall (CMRP - UOW), A. Fazzi(PoliMi), E. Sagia (PoliMi)

Description:

In this part of the experiment, the dE-E stage M1 prototype detector was placed at different depths of a PMMA phantom and was irradiated in order to acquire the microdosimetric spectra along the pristine and the SOBP. These measurements are supplementary to the ones performed in the first experiment. A Dose Magnified Glass (DMG) based on an array of strip detectors was used for measurement of C ion range in PMMA (or water). This new, unique method was proposed for fast QA (quality assurance) measurements of energy verification and penumbra, for ion therapy with C-12.

Third experiment

Date: 30 April 2014

Experiment Leader: A. Rozenfeld (CMRP - UOW), S. Agosteo (PoliMi)

Participants: D. Prokopovich (ANSTO), L.T. Tran (CMRP - UOW)

Description:

An ultra-thin (10 µm thick) 3D detector with a thinned wafer and large active area, as well as a new CMRP SOI microdosimeter (3D mesa "bridge", 4th generation) were used to measure microdosimetric spectra along and downstream of the SOBP. Based on the microdosimetric spectra, the dose mean lineal energy yD was obtained and the RBE10 was derived along the beam axis and downstream of SOBP. The obtained RBE10 was compared with the values obtained by the TEPC under the same experimental conditions.

A MOSkin detector developed at CMRP was investigated for possible fast RBE estimation in C-12 ion beam. Five MOSkins sensors were placed along the beam axis at various depths in the PMMA phantom and were read out in real time. The threshold voltage shift corresponding to the dose delivered to the detector at a given depth was measured. The correlation between the sensitivity of the MOSkin and the RBE was investigated.

An ionisation chamber was used to measure the physical dose along the SOBP in the PMMA phantom in order to compare it with the results obtained by microdosimeters, MOSkin, and Dose Magnified Glass.

HIT

Heidelberg, Germany

General information

The ARDENT collaboration submitted an application for beam time via ULICE in February 2013.

Part of the beam time allocated to ARDENT is for the HIT facility in Heidelberg.

A description of the proposed experiments can be found here:

Get as PDF



A list of publications written with results from the ULICE campaigns (at CNAO and HIT) can be found here:

List of publications



First experiment

Date: 24-26 January 2014 (3 night shifts)

Experiment Leader: Benedikt Bergmann (CTU)

Participants: Ivan Caicedo, Benedikt Bergmann (ARDENT ESRs, CTU), Vaclav Kraus, Michal Holik (CTU)

Technical support: Stefan Brons, Timo Strecker (HIT)

Description:

Timepix detectors have been irradiated with different ion species, i.e. protons, carbon ions, oxygen ions and alpha particles. The detector responses have been investigated for different energies, different angles and different sensor thicknesses (1 mm, 300 μm). The typical intensities of the beams used for clinical purposes had been way too high to separate the interactions of each individual particle and thus were reduced to approximately 104 particles per cm2.

Moreover, a prototype of the device which is going to be installed in the ATLAS detector, has been tested. This device comprises two silicon sensor layers (thicknesses 300 μm and 500 μm) with converter foils, dedicated to neutron detection, in between. This two layer design will allow the discrimination of charged particles and neutrons by evaluating anti- and coincidences, respectively.

The secondary radiation has been monitored by a stack consisting of two 300 μm thick sensors and the RISESAT device. The RISESAT device has been designed in IEAP at CTU and is going to be used as radiation monitor in open space.

CR-39 passive track detectors have been placed outside the beam and close to Timepix detectors to compare the track shapes and the LET of the detectors.

In parallel, measurements estimating the rate of read out failures and single event upsets due to radiation have been performed.

INFN-LNL

Legnaro, Italy

General information

The ARDENT collaboration submitted an application for beam time in June 2013 and in December 2013. Two shifts of 2 days were allocated to ARDENT in the period from December to January 2014.

We are waiting to know if beam time will be allocated in the period from March to June 2014.

A description of the proposed experiments can be found here:

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If you would like to take part in these measurement campaigns, please contact Matteo Magistris (CERN) or Marco Silari (CERN)

Access to LNL will require a certificate from your radiation protection service and a special form to be filled: Registration as LNL users

LNL Annual Report 2014: Go to page 170 to find ARDENT contribution to LNL Annual Report 2014.

First experiment

Date: 12-13 December 2013

Experiment leader: Fabrizio Murtas (CERN)

Participants: E. Frojdh, S. George, M. Magistris, F. Murtas (CERN), and G. D'Angelo, E. Sagia (PoliMi)

Description:

This first experiment focussed on the measurement of a neutron field with the Timepix detector. Three Timepix chips were used, covered with polyethylene and boron converter layers to measure fast and thermal neutrons respectively. Protons produced by the polyethylene were successfully measured. After producing a thermalised neutron field using a block of polyethylene, alpha particles and Li nuclides produced by the interaction of thermal neutrons with the boron converter were also measured. This experiment suggests that discrimination is possible between the alphas and Li nuclei, and the residual protons emitted by the polyethylene block. This discrimination is based on a cut in TOT (energy) and cluster size.

Second experiment

Date: 16-17 January 2014

Experiment leader: Marco Silari (CERN)

Participants: E. Frojdh, S. George, F. Murtas and M. Silari (CERN)

Description:

In this second experiment, two GEMPIX were irradiated in order to measure the neutron field. Long characteristic tracks which appeared to originate from recoil protons produced by the neutron field were identified. A series of gain and drift scans were carried out in order to further understand the performance of the detector when used with a tissue equivalent gas. On insertion of a small plastic target inside the detector, secondary particles emerging from the target were visible. Future experimentation will repeat this procedure with a tissue equivalent target. The neutron field was also thermalised and - by inserting a thin boron 10 target - a new and distinct track was detected, possibly alpha particles or Li nuclei from 10B thermal neutron capture.

INFN-LNS

Catania, Italy

General information

The ARDENT collaboration submitted an application for beam time in March 2013.

A description of the proposed experiments can be found here:

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Eight shifts have been allocated to ARDENT for 2014. The first experiment took place on November 15th-17th.

First experiment

Date: 15 - 17 November 2014 (14:00 - 8:00)

Participants: A. Fazzi (PoliMi), E. Sagia (PoliMi) and A. Sashala Naik (Miam)

Description:

A pixelated silicon-telescope microdosimeter was placed inside a PMMA phantom at different depths and was irradiated with a 62 MeV/u carbon ion beam. Microdosimetric spectra were collected along the Bragg peak with a step of 50 μm, in order to repeat (for verification of reproducibility) and to complete measurements that had been performed in the past at the same facility under the same conditions. Additional measurements were performed at various depths. In particular, signals were collected from both the ΔΕ and E stages without any trigger in order to study the shapes of the different signals collected by the ΔΕ stage while performing measurements in high intensity fields. Stacks of CR-39 detectors were placed in the 62 MeV/u carbon beam to measure the position of the Bragg peak. The track analysis system allows the evaluation of the LET distribution, as well as of the adsorbed dose (mGy) and dose equivalent (mSv) along the beam path. Track detectors with wide area (>10 cm2) were positioned to cover both the in-beam and the off-beam region. Thanks to this arrangement a map was obtained with the dose delivered to target tissues and also to surrounding healthy tissues. The results will be compared with the data obtained by other detectors in the frame of this experiment in carbon ion beams. Neutron dosimeters based on the CR-39 track detector were also tested. They were placed around the PMMA phantom to measure the neutron dose distribution around the phantom.

If you would like to take part in these measurement campaigns, please contact Matteo Magistris (CERN) or Marco Silari (CERN)

MRI

Munich, Germany

General information

In the framework of the ARDENT project, ESR11 Michele Togno had the opportunity to perform the experimental characterization of a novel detector based on ion-chamber technology in two irradiation facilities: the Proton Therapy Center Czech s.r.o. in Prague (see experiment in Prague) and the Klinikum rechts der Isar in Munich. Two shifts of approximately 4 hours each were allocated to the experiment in Munich.

Experiment

Date: 28 April, 30 April 2014

Experiment Leader: Michele Togno (IBA Dosimetry) (IBA Dosimetry)

Participants: Michele Togno (IBA Dosimetry), Markus Oechsner (Klinikum rechts der Isar)

Description:

This experimental session focused on the characterization of the ion-chamber detector prototype under clinical beams of photons and electrons. The major objective was to assess whether the developed technology is able to fulfill the requirements of quality assurance and treatment plan verifications in contemporary complex treatment techniques.

Measurements were performed with a Varian Clinac DHX accelerator, featuring two photon beam qualities (6 MV and 15 MV, only flattened), 600 MU/min of maximum dose rate and the possibility to deliver IMRT and VMAT radiotherapy treatments. Two different set of measurements were carried out:

- Accelerator quality assurance: the detector was positioned at a 3 cm water-equivalent depth and different radiation fields were delivered, changing the field size, the spatial dose distribution and the total dose. The outcomes were compared with the reference detector used in the clinic (PTW MapCheck2, based on diode technology).

- Treatment plan verification: a tomography of the detector was acquired an uploaded into the planning system to determine the theoretical dose distribution. Then both IMRT and VMAT treatment fractions were delivered to the detector positioned into a PMMA phantom. At the end, results from the ion-chamber array, estimated dose distributions from the planning system and results from measurements with self-developing Gafchromic films in the same experimental conditions were compared.

PTC

Prague, Czech Republic

General information

In the framework of the ARDENT project, ESR11 Michele Togno had the opportunity to perform the experimental characterization of a novel detector based on ion-chamber technology in two irradiation facilities: the Proton Therapy Center Czech s.r.o. in Prague and the Klinikum rechts der Isar in Munich (see experiment in Munich). One shift of approximately 8 hours was allocated in Prague to the first experiment and five shifts of 5 hours to the second one.

First Experiment

Date: 15-16 February 2014

Experiment Leader: David Menichelli (IBA Dosimetry)

Participants: David Menichelli, Michele Togno, Patrick Takoukam, Juan Carlos Celi (IBA Dosimetry)

Technical support: Michal Bystersky, Martin Hejzlar, Mikhail Frolov (IBA Particle Therapy)

Description:

This experimental session focused on the characterization of the ion-chamber detector prototype under clinical proton beams. Since QA procedures in proton therapy differ from those of conventional radiotherapy techniques (electrons and photons), this preliminary investigation was carried out in order to determine whether this technology is suitable for QA in proton therapy. Measurements were performed in a 360° gantry treatment room, with beam delivered in Pencil Beam Scanning mode. With this delivery technique, the main beam features are: 1 ms pulse duration, 10 ms pulse period and about 3.8 mm spot standard deviation at 226 MeV at isocenter. The detector was irradiated from 0° gantry angle, positioned at a water-equivalent measurement depth of 11 mm. The investigations performed on the device include: charge collection efficiency dependence on bias voltage, linearity with energy (in the range 98-226 MeV) and linearity with dose (in the range 0.02-2 MU/spot, with 226 MeV beam energy and 5 nA beam current to detector kept fixed). Furthermore, the one-dimensional dose distribution for different spot maps was measured at a defined beam quality and cyclotron current. The measurements were repeated in the same experimental conditions with two reference detectors (IBA MatriXX PT, based on ion-chamber technology, and IBA Lynx PT, based on scintillator technology) and the outcomes were compared.

Second Experiment

Date: 17 February - 18 March 2015

Experiment Leader: Michele Togno (IBA Dosimetry) (IBA Dosimetry)

Participants: Michele Togno (IBA Dosimetry), Anna Michaelidesova and Vladimir Vondracek (Department of medical physics, Proton Therapy Center Czech s.r.o.)

Description:

These experimental sessions focused on the characterization of the ion-chamber detector prototype with clinical proton beams. Measurements were performed in a 360° gantry treatment room, with beam delivered in Pencil Beam Scanning mode. With this delivery technique, the main beam features are: 1 ms pulse duration, 10 ms pulse period and about 3.8 mm spot standard deviation at 226 MeV at isocenter. The detector was irradiated from 0° gantry angle. Measurements of basic dosimetric performances were performed again to check the detector repeatability. Such investigations include: charge collection efficiency dependence on bias voltage at the maximum available treatment current (i.e. 6.2 nA), linearity with dose and dose rate at three different energies (i.e. 100, 165 and 226 MeV) in the range 5 cGy to 30 Gy (dose rate up to 12 MU/min).

Moreover, the characterization of some beam features was performed:

  • Measurements of one dimensional dose distributions for different spot maps and different energies (reference detectors IBA MatriXX PT and IBA Lynx PT)
  • Measurements of depth dose curves of pristine Bragg peak at different energies (reference detector PTW Bragg peak chamber)

Additionally, the characterization of high dose gradients was carried out by delivering selected patient plans. The measured distribution was compared with both the treatment planning system output and the commercial ion chamber array MatriXX PT.

WNR, LANSCE

Los Alamos, New Mexico, USA

General information

Proposals were successfully submitted by our colleagues from the Brookhaven National Laboratory for beam time at the Weapon Neutron Research facility of the Los Alamos Neutron Science Center. The main purpose of the measurements were radiation hardness studies of electronic components. However, we were able to use the beam parasitically for measurements with our detectors. At the weapon neutron research facility of the Los Alamos Neutron Science Center, an 800 MeV pulsed proton beam is directed onto a cylindrical tungsten target. The bunched proton beam is divided into 625 µs long macro-pulses, that consist of sharp micro-pulses (FWHM: ~125 ps) separated by 1.8 µs. In a spallation process 10-20 neutrons per incoming proton are created. Charged particles are separated from the neutron beam by a magnetic field, so that a clean neutron beam in the energy range from a few hundreds of keV up to 600 MeV is delivered to several flight paths. The Time-of-Flight technique was used to assign the detector responses to incident neutron energy.

First experiment

Date: February 10-19, 2013

Experiment leader: Zdenek Vykydal

Participants: Benedikt Bergmann, Stanislav Pospisil, Zdenek Vykydal.

Description:

The data were taken in the ICE House II at the flight path 30 left. The distance of the detector to the interaction point was approximately 15 m. A Timepix device with a sensitive silicon layer of 300 µm thickness with converter layers was irradiated by the neutron beam. The layout of the converter foils was the same as the layout of the devices that were installed in the ATLAS experiment within the Medipix detector network. The data was used to calibrate the efficiencies below each of the converter layers and to validate MCNPX simulations. The setup and the data evaluation technique are described in greater detail in B. Bergmann et al. , "Time-of-Flight Measurement of Fast Neutrons with Timepix Detectors", JINST 9 C05048, 2014.

Second experiment:

Date: December 1-8, 2013

Experiment leader: Zdenek Vykydal

Participants: Benedikt Bergmann, Daniel Turecek, Zdenek Vykydal

Description:

The below described detectors and setups were placed at a distance of 20 m to the interaction point at the neutron flight path 30 right. A Timepix detector with a 1 mm thick sensor layer was irradiated to study the interactions of neutrons in the silicon itself. The ToA mode was used in order to assign the neutron energies according the ToF-technique. A prototype of the ATLAS hodoscope (a Timepix stack consisting of 300 µm and 500 µm thick silicon sensor layers with converter foils in between, specifically designed for use in the ATLAS experiment) was tested. Data were taken at different angles with two different modes of operation: Time of Arrival (ToA) and Time over Threshold (ToT). Due to problems with the LANSCE Linac, the beam was only available for 1.5 days with reduced fluence. CR39 foils with 1 cm of PE were irradiated to be used for an intercomparison.

Third Experiment:

Date: December 4-7, 2014

Experiment leader: Benedikt Bergmann

Participants: Erik Frojdh, Stanislav Pospisil, Daniel Turecek, Benedikt Bergmann.

Description:

Several detectors and setups were tested. These include the ATLAS hodoscope, the TPX3 with a Fitpix readout and a Timepix device with a 1 mm thick sensor layer at the flight path 30 right in a distance of 20 m from the interaction point. The ATLAS hodoscope was placed in the beam and rotated. The angles range from 0° to 180° was investigated stepwise in steps of 30°. This data will be used to calibrate the efficiencies for neutron detection and to correlate the responses below different converter foils to the corresponding neutron energies. The detector was used in the ToT and the ToA mode. A beam test was performed with the Timepix3. For the first time at a beam line the data was readout with a Fitpix device. The data taking was triggered and the focus of the data evaluation will be on the estimation of the performance of the Timepix3 and the discovery of bugs of the readout. Moreover, CR39 tracking foils were irradiated for intercomparison measurements. The foils were irradiated at different angles. In order to keep the occupancy of tracks in the foils low, the devices could be irradiated only for short periods of time (i.e., a few seconds).

PTC

Prague, Czech Republic

General description

The Van de Graaff HV2500 accelerator (VdG) provides light ions (p,d,4He, newly also 12, 14N) with energy in the range 0.2-2.3 MeV as well as mono-energetic fast neutrons of tunable energy in selected ranges from 30 keV up to 19 MeV. The RI is used for both basic and applied multi-disciplinary research in subatomic physics, material physics and space research. Experiments installed or being completed at the VdG RI include polarized tagged neutron beam/polarized target setup for spin physics, tagged neutron beam, low-energy nuclear reactions for fusion and astrophysical research and material surface analysis by RBS and PIXE methods. In applied research the accelerator serves for radiation effects studies in electronic devices as well as calibration and testing facility of detectors and radiation sensitive devices providing well-defined fields of light ions and fast and resonance neutrons. The beam/sources energy ranges and intensities/fluxes are given in the annexed table.

Use and access to the VdG beams and neutron sources is open-access. Users from academia and scientific community are welcome. Beam is provided free of cost for research and scientific purposes. Beam time requests are submitted 1 month ahead (1-page form available at the webpage). Contact to Carlos Granja or Michael Solar. Visit the official website here.

WPE

Essen, Germany

General description

Some of the ARDENT ESRs were invited to perform measurements in the West German Proton Therapy Centre of Essen (WPE) with Bonner Sphere Spectrometers, with a view to measuring the neutron spectra in various positions and comparing the results to those obtained with detectors by other researchers taking part in the same experiment.

Experiment

Date: April 5-6, 2014

Participants from ARDENT: E. Aza (CERN), C. Cassel (PoliMi)

Participating Institutions (Belgium): IBA, SCK-CEN, IRISIB, IIHE-ULB

This experiment took place inside and outside a Fixed-beam Treatment Room, where a wide neutron spectrum was generated by a 230 MeV proton beam impinging on a water phantom. The neutron spectra were measured with a set of seven Bonner Spheres, including two extended-range ones (C. Birattari et. al, NIM A620, pp 260-269). The spectrometry measurements were performed with two types of active acquisition systems using a 3He proportional counter coupled to either conventional electronics or LUPIN-type electronics. Measurements were performed in two positions inside the treatment room, two positions in the adjacent technical room and in several positions along the maze giving access to the room.

The data acquired were unfolded with three programs (MAXED, GRAVEL and FRUIT) and will be compared to simulated spectra obtained with MCNPX. The neutron spectra will be folded with the fluence-to-H*(10) conversion function to obtain the neutron H*(10) rate, which will be compared to the other measurements performed with different types of rem counters and a TEPC.