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Background In Monte Carlo simulations, the fine-tuning of linac beam parameters to produce a good match between simulated and measured dose profiles is a lengthy, time-consuming and resource-intensive process. The objective of this study is to utilize the results of the gamma-index analysis toolkit embedded inside the windows-based PRIMO software package to yield a truncated linac photon beam fine-tuning process. Methods Using PRIMO version 0.1.5.1307, a Varian Clinac 2100 is simulated at two nominal energy configurations of 6 MV and 10 MV for varying number of histories from 106 to more than 108. The dose is tallied on a homogeneous water phantom with dimensions 16.2 × 16.2 × 31.0 cm3 at a source-to-surface-distance of 100.0 cm. For each nominal energy setting, two initial electron beam energies are configured to reproduce the measured percent depth dose (PDD) distribution. Once the initial beam energy is fixed, several beam configurations are sequentially simulated to determine the parameters yielding good agreement with the measured lateral dose profiles. The simulated dose profiles are compared with the Varian Golden Beam Data Set (GBDS) using the gamma-index analysis method incorporating the dose-difference and distance-to-agreement criteria. The simulations are run on Pentium-type computers while the tuned 10 MV beam configuration is simulated at more than 108 histories using a virtual server in the Amazon.com Elastic Compute Cloud. Results The initial electron beam energy configuration that will likely reproduce the measured PDD is determined by comparing directly the gamma-index analysis results of two different beam configurations. The configuration is indicated to yield good agreement with data if the gamma-index passing rates using the 1%/1 mm criteria generally increase as the number of histories is increased. Additionally at the highest number of histories, the matching configuration gives a much higher passing rate at the 1%/1 mm acceptance criteria over the other competing configuration. With the matching initial electron beam energy known, this input to the subsequent simulations allows the fine-tuning of the lateral beam profiles to proceed at a fixed yet lower number of histories. In a three-stage serial optimization procedure, the first remaining beam parameter is varied and the highest passing rate at the 1%/1 mm criteria is determined. This optimum value is input to the second stage and the procedure is repeated until all the remaining beam parameters are optimized. The final tuned beam configuration is then simulated at much higher number of histories and the good agreement with the measured dose distributions is verified. Conclusions As physical nature is not stingy, it reveals at low statistics what is hidden at high statistics. In the matter of fine-tuning a linac to conform with measurements, this characteristic is exploited directly by the PRIMO software package. PRIMO is an automated, self-contained and full Monte Carlo linac simulator and dose calculator. It embeds the gamma-index analysis toolkit which can be used to determine all the parameters of the initial electron beam configuration at relatively lower number of histories before the full simulation is run at very high statistics. In running the full simulation, the Amazon.com compute cloud proves to be a very cost-effective and reliable platform. These results are significant because of the time required to run full-blown simulations especially for resource-deficient communities where there could just be one computer as their sole workhorse.

The Philippines is an archipelagic country with an estimated 105 M people. Although cancer is the third leading cause of mortality, only a few radiotherapy centers are in operation and majority of these are located in the capital region of Manila in the island of Luzon. There is only a single school, a private university, located in Manila, offering the master’s degree in medical physics. Mindanao Island, considered the breadbasket of the nation, is the second largest island of the Philippines. It is located in the south and has a population of about 22 M people. Only four hospitals in Mindanao provide radiotherapy services using a linear accelerator (linac) while four radiation oncologists and seven medical physicists serve the needs of the entire island. We describe in this paper the public-private partnership (PPP) strategy we are proposing in order to acquire a medical linac to be used for radiotherapy at a local private hospital, for research, and for a planned medical physics education and training program in the largest state university in Mindanao.

PRIMO is a free, self-contained linac simulator and dose calculation software based on the Monte Carlo code PENELOPE 2011. Windows-based, it is user-friendly and does not require any programming tasks by the end user. PRIMO comes with an intuitive graphical interface which guides the configuration and execution of the linac simulation in seemingly natural stages: from the primary electron source in the linac head to the collimators then down to a binned water phantom or patient computed tomography. We report here the simulations done with PRIMO of a 6 MV Varian Clinac 2100 and the dose deposition in a water phantom using student desktop computers with Pentium type processors. The program is then ported to the Amazon Elastic Compute Cloud. Here abnormal program termination due to power outages which is a common occurrence in developing countries is no longer a concern. Without the need to invest in expensive hardware upfront, the PRIMO simulations can be deployed reliably and faster in the Amazon Cloud and which for some time can be free.

A new sampling calorimeter using very thin scintillators and the multi-pixel photon counter (MPPC) has been proposed to produce better position resolution for the international linear collider (ILC) experiment. As part of this R&D study, small plastic scintillators of different sizes, thickness and wrapping reflectors are systematically studied. The scintillation light due to beta rays from a collimated 90Sr source are collected from the scintillator by wavelength-shifting (WLS) fiber and converted into electrical signals at the PMT.

R&D studies on the performance as well as on the gas properties of the microMEGAS-based time projection chamber with standard readout were carried out in June 2005 using 4 GeV/c pion beam in a magnetic field from 0 to 1 T at the proton synchrotron beam line at KEK, Japan. Analysis of the electron drift velocity, diffusion constant and point resolution of padrow measurement for MicroMEGAS TPC filled with 95% argon and 5% isobutane gas are presented. The underlying physical mechanism which determines the optimal TPC performance are briefly discussed. Preliminary measurements of gas properties and spatial resolution in close agreement with the analytical calculation and MAGBOLTZ simulation are summarized and presented in this paper.

We have studied, using cosmic rays, the influence of oxygen contamination on the performance of a test drift chamber filled with a CO2:iso-C4H10 (90:10) gas mixture. The test chamber has the same mini-jet-cell structure as our proposed central tracker for JLC (JLC-CDC). We observed significant deterioration of its spatial resolution with oxygen contamination in the long drift region, though the wire efficiency stayed essentially 100% up to 50 ppm of oxygen over the full drift length of 5 cm . From the drift-time dependence of signal charge, we evaluated the electron attachment rates at different oxygen concentrations. The results were found to be consistent with a proposed empirical expression for the attachment of thermal electrons.

We have studied K S 0 K S 0 production in the interactions of a virtual photon ( Q 2 >0) with a real photon and observed the resonance production of f 2 ′ (1525). A total of 5.0±2.2(sta)±0.5(sys) f...

We present the results of a study of e + e − μ + μ − final states produced in e + e − collisions at a center-of-mass energy of 58 GeV using the AMY detector at TRISTAN. The data correspond to a total integrated luminosity of 292.8 pb −1 . The results show good agreement with order α 4 QED predictions.

We observe ηc production in the two photon process e+e−→e+e−ηc at an e+e− center-of-mass energy of 58 GeV. We determine the radiative decay width Γγγ(ηc) to be 27±16(sta)±10(sys) keV.

International audience; A time projection chamber (TPC) is a strong candidate for the central tracker of the international linear collider (ILC) experiment and we have been conducting a series of cosmic ray experiments under a magnetic field up to 4 T, using a small prototype TPC with a replaceable readout device: multi-wire proportional chamber (MWPC) or gas electron multiplier (GEM). We first confirmed that the MWPC readout could not be a fall-back option of the ILC-TPC under a strong axial magnetic field of 4 T since its spatial resolution suffered severely from the so called E×B effect in the vicinity of the wire planes. The GEM readout, on the other hand, was found to be virtually free from the E×B effect and gave the resolution determined by the transverse diffusion of the drift electrons (diffusion limited). Furthermore, GEMs allow a wider choice of gas mixtures than MWPCs. Among the gases we tried so far a mixture of Ar–CF4-isobutane seems promising as the operating gas of the ILC-TPC because of its small diffusion constant especially under a strong magnetic field. We report the spatial resolution obtained with the GEM readout in this gas mixture. Also presented is the spatial resolution of a GEM-based ILC-TPC estimated from the measurement with the prototype.

International audience; We conducted a series of beam tests of prototype TPCs for the International Linear Collider (ILC) experiment, equipped with an MWPC, a MicroMEGAS, or GEMs as a readout device. The prototype operated successfully in a test beam at KEK under an axial magnetic field of up to 1 T. The analysis of data is now in progress and some of the preliminary results obtained with GEMs and MicroMEGAS are presented along with our interpretation. Also given is the extrapolation of the obtained spatial resolution to that of a large TPC expected as the central tracker of the ILC experiment.

The results of a beam test performed at the KEK PS in June 2005 are presented. Drift properties of an argon-isobutane mixture have been accurately measured and compared with predictions at magnetic fields between 0 and 1 Tesla. The r.m.s. point resolution of a padrow is compared with simulation and with an analytical calculation. The fundamental limitations due to detector geometry and gas properties are reviewed and the measured performances of the detector are found to be close to this limit. A numerical application to the case of a Linear Collider TPC is presented., Comment: To be submitted to NIM A, 25 pages