D. Pinci

Performance of the LHCb muon system

The performance of the LHCb Muon system and its stability across the full 2010 data taking with LHC running at root s = 7 TeV energy is studied. The optimization of the detector setting and the time calibration performed with the first collisions delivered by LHC is described. Particle rates, measured for the wide range of luminosities and beam operation conditions experienced during the run, are compared with the values expected from simulation. The space and time alignment of the detectors, chamber efficiency, time resolution and cluster size are evaluated. The detector performance is found to be as expected from specifications or better. Notably the overall efficiency is well above the design requirements.

Toward Radioguided Surgery with β− Decays: Uptake of a Somatostatin Analogue, DOTATOC, in Meningioma and High-Grade Glioma

A novel radioguided surgery (RGS) technique for cerebral tumors using β− radiation is being developed. Checking for a radiotracer that can deliver a β− emitter to the tumor is a fundamental step in the deployment of such a technique. This paper reports a study of the uptake of 90Y-DOTATOC in meningiomas and high-grade gliomas (HGGs) and a feasibility study of the RGS technique in these types of tumor. Estimates were performed assuming the use of a β− probe under development with a sensitive area 2.55 mm in radius to detect 0.1-mL residuals. Methods: Uptake and background from healthy tissues were estimated on 68Ga-DOTATOC PET scans of 11 meningioma patients and 12 HGG patients. A dedicated statistical analysis of the DICOM images was developed and validated. The feasibility study was performed using full simulation of emission and detection of the radiation, accounting for the measured uptake and background rate. Results: All meningioma patients but one with an atypical extracranial tumor showed high uptake of DOTATOC. In terms of feasibility of the RGS technique, we estimated that by administering a 3 MBq/kg activity of radiotracer, the time needed to detect a 0.1-mL remnant with 5% false-negative and 1% false-positive rates is less than 1 s. Actually, to achieve a detection time of 1 s the required activities to administer were as low as 0.2–0.5 MBq/kg in many patients. In HGGs, the uptake was lower than in meningiomas, but the tumor-to-nontumor ratio was higher than 4, which implies that the tracer can still be effective for RGS. It was estimated that by administering 3 mBq/kg of radiotracer, the time needed to detect a 0.1-mL remnant is less than 6 s, with the exception of the only oligodendroma in the sample. Conclusion: Uptake of 90Y-DOTATOC in meningiomas was high in all studied patients. Uptake in HGGs was significantly worse than in meningiomas but was still acceptable for RGS, particularly if further research and development are done to improve the performance of the β− probe.

Contributions of Cherenkov light to the signals from lead tungstate crystals

Results are presented of detailed measurements of the signals generated by high-energy electrons and muons in lead tungstate crystals. A significant fraction of the light produced in these crystals and detected by photomultiplier tubes is the result of the Cherenkov mechanism. This is concluded from the angular dependence of the signals and from their time structure. Depending on the orientation of the crystals and on the particle type, Cherenkov light may account for up to 15% of the total signals. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Ka; 29.40.Mc; 29.40.Vj

Measurement of the contribution of neutrons to hadron calorimeter signals

The contributions of neutrons to hadronic signals from the DREAM calorimeter are measured by analyzing the time structure of these signals. The neutrons, which mainly originate from the evaporation stage of nuclear breakup in the hadronic shower development process, contribute through elastic scattering off protons in the plastic scintillating fibers which provide the dE=dx information in this calorimeter. This contribution is characterized by an exponential tail in the pulse shape, with a time constant of � 25 ns. The relative contribution of neutrons to the signals increases with the distance from the shower axis. As expected, the neutrons do not contribute to the DREAM Cherenkov signals. r 2007 Elsevier B.V. All rights reserved. PACS: 29.40.Ka; 29.40.Mc; 29.40.Vj

A complete simulation of a triple-GEM detector

Since some years the gas electron multipliers (GEM)based detectors have been proposed for many different applications, in particular, in high-energy physics and astrophysics experiments and medical imaging. Many experimental measurements and tests have been performed to investigate their characteristics and performances. To achieve a better understanding of the behavior of this kind of detector the computer simulation is a very important tool. In this paper, a complete and detailed simulation of a triple-GEM-based detector is described. A method has been developed to take into account all the processes from the ionization mechanism up to the signal formation and electronic response. The results obtained are compared with experimental data and a very good agreement is achieved.

Time-multiplexing of signal using highly integrated digital delay: an FPGA implementation

We have designed and implemented on a Xilinx SpartanIIE FPGA a highly integrated time-multiplexing device by means of using multiple fixed delays. Signals coming from MWPCs (multi wire proportional chambers) front end readout circuitry can be multiplexed in time using selected delay values. Up to 5 channels can be merged into one using delays in increments of 150 ns. As a consequence, usage of one multi-hit channel to measure timing of 5 channels is possible. Inside the FPGA a 36 to 8 multiplexing is performed, resulting in a reduction, of more than a factor of four, of the number of multi-hit TDC channels needed.

Quality tests of the LHCb muon chambers at the LNF production site

The performance demanded for the Level-0 trigger of LHCb imposes very stringent requirements on the quality of the muon chambers. These chambers must pass a series of tests before being mounted in the experimental setup. The six tests adopted for the quality control of the chambers produced at the Laboratori Nazionali di Frascati (LNF) are described. After the wires are wound and glued on a cathode panel, the wire pitch is measured by two digital cameras with a precision of about 20 mum. The mechanical tension of the wire is deduced from its mechanical resonance frequency measured by an automated system based on a digital electrostatic method. The wire tension is obtained with a precision of about 1%. Once all elements are assembled, the gas tightness of a chamber is verified by monitoring the decrease rate of an overpressure applied to it. After a suitable high-voltage conditioning, the dark current is recorded and the gas gain uniformity of the chamber is measured using a collimated 137Cs source which can be moved over the chamber surface. Finally, the detector is fully equipped with the front-end electronics, and its detection efficiency is tested with cosmic rays

Secondary radiation measurements for particle therapy applications: prompt photons produced by

Charged particle beams are used in particle therapy (PT) to treat oncological patients due to their selective dose deposition in tissues with respect to the photons and electrons used in conventional radiotherapy. Heavy (Z  >  1) PT beams can additionally be exploited for their high biological effectiveness in killing cancer cells. Nowadays, protons and carbon ions are used in PT clinical routines. Recently, interest in the potential application of helium and oxygen beams has been growing. With respect to protons, such beams are characterized by their reduced multiple scattering inside the body, increased linear energy transfer, relative biological effectiveness and oxygen enhancement ratio. The precision of PT demands online dose monitoring techniques, crucial to improving the quality assurance of any treatment: possible patient mis-positioning and biological tissue changes with respect to the planning CT scan could negatively affect the outcome of the therapy. The beam range confined in the irradiated target can be monitored thanks to the neutral or charged secondary radiation emitted by the interactions of hadron beams with matter. Among these secondary products, prompt photons are produced by nuclear de-excitation processes, and at present, different dose monitoring and beam range verification techniques based on prompt-γ detection are being proposed. It is hence of importance to perform γ yield measurement in therapeutic-like conditions. In this paper we report on the yields of prompt photons produced by the interaction of helium, carbon and oxygen ion beams with a poly-methyl methacrylate (PMMA) beam stopping target. The measurements were performed at the Heidelberg Ion-Beam Therapy Center (HIT) with beams of different energies. An LYSO scintillator, placed at [Formula: see text] and [Formula: see text] with respect to the beam direction, was used as the photon detector. The obtained γ yields for the carbon ion beams are compared with results from the literature, while no other results from helium and oxygen beams have been published yet. A discussion on the expected resolution of a slit camera detector is presented, demonstrating the feasibility of a prompt-γ-based monitoring technique for PT treatments using helium, carbon and oxygen ion beams.

^{4}

Bolometers have proven to be good instruments to search for rare processes because of their excellent energy resolution and their extremely low intrinsic background. In this kind of detectors, the capability of discriminating alpha particles from electrons represents an important aspect for the background reduction. One possibility for obtaining such a discrimination is provided by the detection of the Cerenkov light which, at the low energies of the natural radioactivity, is only emitted by electrons. In this paper, the results of the analysis of the light emitted by a TeO2 crystal at room temperature when transversed by a cosmic ray are reported. Light is promptly emitted after the particle crossing and a clear evidence of its directionality is also found. These results represent a strong indication that Cerenkov light is the main, if not even the only, component of the light signal in a TeO2 crystal. They open the possibility to make large improvements in the performance of experiments based on this kind of materials.

He,

Nowadays there is a growing interest in particle therapy treatments exploiting light ion beams against tumors due to their enhanced relative biological effectiveness and high space selectivity. In particular promising results are obtained by the use of 4He projectiles. Unlike the treatments performed using protons, the beam ions can undergo a fragmentation process when interacting with the atomic nuclei in the patient body. In this paper the results of measurements performed at the Heidelberg Ion-Beam Therapy center are reported. For the first time the absolute fluxes and the energy spectra of the fragments-protons, deuterons, and tritons-produced by 4He ion beams of 102, 125 and 145 MeV u-1 energies on a poly-methyl methacrylate target were evaluated at different angles. The obtained results are particularly relevant in view of the necessary optimization and review of the treatment planning software being developed for clinical use of 4He beams in clinical routine and the relative bench-marking of Monte Carlo algorithm predictions.