Beam profiling during patient treatment in protontherapy requires ultra-thin monitors to preserve the high beam quality. For detectors upstream in the line, a material budget as low as ∼ 15 μm ...water-equivalent is needed. In addition, the current trend of dose escalation to treat highly resistant tumors implies challenging requirements on monitor radiation hardness and dynamic range. We propose a new type of beam profiler, PEPITES, using secondary electron emission (SEE) and built with thin-film techniques. The beam is profiled by crossing a pattern or a series of patterns which emit the SEE signal and can be made ultra-thin as SEE originates from the few nanometers next to the surface. The patterns are deposited on membranes, which, in contrast with common systems like ionization chambers, are free from mechanical constraints and can then afford higher absorbed doses and be as thin as achievable. A simple demonstrator prototype has been built and successfully operated with a proton beam at the ARRONAX cyclotron at St Herblain in a wide range of currents (100 fA to 10 nA) and several energies (30 - 68 MeV). Beam profiling results from these tests are presented, and our plans for the next prototypes are mentioned.
PEPITES is a new type of transparent beam profiler (<10 µm water-equivalent thickness (WET)) under development that will equip the beam line of the ARRONAX cyclotron. Segmented electrodes consisting ...of nanometric thick gold strips deposited on a thin polymer membrane make the active part. In order to characterize the damages induced in the polymer, UV–Vis spectroscopy and scanning electron microscope have been used on 8 μm thick Kapton polyimide membranes irradiated with 68 MeV proton beams up to 7 × 1015 H+/cm2. Dynamic and permanent damage was observed only at a high fluence level, thus ensuring long-term operation of the PEPITES detector in its nominal working environment.
Operational experience with the DIRC detector Adam, I.; Aleksan, R.; Aston, D. ...
IEEE Transactions on Nuclear Science,
06/2002, Letnik:
49, Številka:
3
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The DIRC, a novel type of Cherenkov ring imaging device, is the primary hadronic particle identification system for the BABAR detector at the asymmetric B-factory, PEP-II at the Stanford Linear ...Accelerator Center. It is based on total internal reflection and uses long, rectangular bars made from synthetic fused silica as Cherenkov radiators and light guides. BABAR began taking data with colliding beams in late spring 1999. This paper describes the performance of the DIRC during the first 2.5 years of operation.
A search for the standard model Higgs boson decaying to W+W- in pp collisions at sqrt(s) = 7 TeV is reported. The data are collected at the LHC with the CMS detector, and correspond to an integrated ...luminosity of 4.6 inverse femtobarns. The W+W- candidates are selected in events with two charged leptons and large missing transverse energy. No significant excess of events above the standard model background expectations is observed, and upper limits on the Higgs boson production relative to the standard model Higgs expectation are derived. The standard model Higgs boson is excluded in the mass range 129-270 GeV at 95% confidence level.
Recent results from the Front-End electronics of the Detector of Internally Reflected Cerenkov light (DIRC) for the BaBar experiment at SLAC (Stanford, USA) are presented. It measures to better than ...1 ns the arrival time of Cerenkov photoelectrons detected in a 11000 phototubes array and their amplitude spectra. It mainly comprises 64-channel DIRC Front-End Boards (DFB) equipped with eight full-custom analog chips performing zero-cross discrimination with 2 mV threshold and pulse shaping, four full-custom digital time to digital chips (TDC) for timing measurements with 500 ps binning and a readout logic selecting hits in the trigger window, and DIRC Crate Controller cards (DCC) serializing the data collected front up to 16 DFBs onto a 1.2 Gb/s optical link. Extensive test results of the pre-production chips are presented, as well as system tests.
A search for the standard model Higgs boson decaying into two Z bosons with subsequent decay into a final state containing two quark jets and two leptons, H to ZZ(*) to q q-bar l-l+ is presented. ...Results are based on data corresponding to an integrated luminosity of 4.6 inverse femtobarns of proton-proton collisions at sqrt(s)=7 TeV, collected with the CMS detector at the LHC. In order to discriminate between signal and background events, kinematic and topological quantities, including the angular spin correlations of the decay products, are employed. Events are further classified according to the probability of the jets to originate from quarks of light or heavy flavor or from gluons. No evidence for the Higgs boson is found, and upper limits on its production cross section are determined for a Higgs boson of mass between 130 and 600 GeV.
The production of b jets in association with a Z/gamma* boson is studied using proton-proton collisions delivered by the LHC at a centre-of-mass energy of 7 TeV and recorded by the CMS detector. The ...inclusive cross section for Z/gamma* + b-jet production is measured in a sample corresponding to an integrated luminosity of 2.2 inverse femtobarns. The Z/gamma* + b-jet cross section with Z/gamma* to ll (where ll = ee or mu mu) for events with the invariant mass 60 < M(ll) < 120 GeV, at least one b jet at the hadron level with pT > 25 GeV and abs(eta) < 2.1, and a separation between the leptons and the jets of Delta R > 0.5 is found to be 5.84 +/- 0.08 (stat.) +/- 0.72 (syst.) +(0.25)/-(0.44) (theory) pb. The kinematic properties of the events are also studied and found to be in agreement with the predictions made by the MadGraph event generator with the parton shower and the hadronisation performed by PYTHIA.
A measurement of the exclusive two-photon production of muon pairs in proton-proton collisions at sqrt(s)= 7 TeV, pp to p mu^+ mu^- p, is reported using data corresponding to an integrated luminosity ...of 40 inverse picobarns. For muon pairs with invariant mass greater than 11.5 GeV, transverse momentum pT(mu) > 4 GeV and pseudorapidity |eta(mu)| < 2.1, a fit to the dimuon pt(mu^+ mu^-) distribution results in a measured cross section of sigma(pp to p mu^+ mu^- p) = 3.38 +0.58 -0.55 (stat.) +/- 0.16 (syst.) +/- 0.14 (lumi.) pb, consistent with the theoretical prediction evaluated with the event generator Lpair. The ratio to the predicted cross section is 0.83 +0.14-0.13 (stat.) +/- 0.04 (syst.) +/- 0.03 (lumi.). The characteristic distributions of the muon pairs produced via photon-photon fusion, such as the muon acoplanarity, the muon pair invariant mass and transverse momentum agree with those from the theory.
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