109046686
Beam incidents - High particle rate tests of an LHCb/Velo silicon strip module
L. Eklund ∗a, K. Akiba b, O. Behrendt c, M. van Beuzekom b, J. Buytaert c, P. Collins c, M. Ferro-Luzzi c, K. Hennessy d, J. Imong e aUniversity of Glasgow, Glasgow, UK. bNikhef, National Institute for Subatomic Physics, Amsterdam, Netherlands. cEuropean Organisation for Nuclear Research (CERN), Geneva, Switzerland. dUniversity of Liverpool, Liverpool, UK eH.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom. E-mail: Lars.Eklund@cern.ch
114023912
Performance of a wide pitch n-on-n silicon detector with floating strips
1648236
The LHCb VELO: status and upgrade developments
The VErtex LOcator (VELO) is the silicon microstrip vertexing and triggering sub-detector of the LHCb experiment. It consists of a series of forward disks with the active region extending to just 8 mm from the LHC beams. The current status of the VELO is presented. Due to the high radiation environment, the VELO may have to be replaced after some years, possibly with new materials. A candidate material is Czochralski silicon. We present here promising new results on the first test beam of a large, high resistivity Czochralski microstrip silicon detector read out with LHC speed electronics. The performance was studied before and after irradiation with high energy protons. A signal to noise of over 20:1 was obtained from the detector and significant charge collection efficiencies were measured at relatively modest voltages after a fluence of 4.3/spl times/10/sup 14/ 1 MeV neutron equivalents (n/sub eq/) per cm/sup 2/. Studies using the Transient Current Technique probed the electric field within MCz test detectors and proved that MCz silicon does not type invert up until a radiation level of at least 5/spl times/10/sup 14/ 24GeV/c p/cm/sup 2/. This would mean the VELO could possibly replace, in a potential upgrade, n/sup +/-on-n DOFZ sensors and the complicated processing involved, for standard p/sup +/-on-n processing with MCz.
208345688
VELO Geometry Optimisation
New possible layouts of the LHCb Vertex Locator (VELO) have been compared with the existing baseline design outlined in the Technical Proposal. Based on a comparison of essential figures of merit, namely vertex resolutions, event selection efficiencies, trigger performance, and technical constraints an updated baseline design is proposed. The new design retains the same number of electronic channels as that in the Technical Proposal, but has an increased number of measuring stations (25 rather than 17) with a reduced inner radius (8mm rather than 10mm).
15273175
The LHCb trigger strategy and performance
Precise measurements of CP-violating asymmetries, oscillation parameters and branching ratios on numerous B-decay channels will allow an overdetermination of CKM parameters, with possible inconsistencies pointing to physics beyond the Standard Model. In order to achieve this, an experiment capable of triggering on the various decay modes of B-mesons (in particular hadronic modes) is desirable. LHCb [ 1] is an experiment dedicated to such precision studies at the large hadron collider (LHC). It is designed as a forward spectrometer, because BB pairs are expected to be predominantly produced at small polar angles. An overview of the LHCb detector and trigger scheme is shown in Figure 1.
121605096
Performance of an irradiated LHCb prototype p-on-n silicon microstrip detector
Abstract A prototype silicon detector for the LHCb experiment has been irradiated non-uniformly with fluences of up to 10 15 p / cm 2 of 24 GeV protons and tested with LHC speed electronics in a test beam. After doses equivalent to one year of operation at the LHC, the detector was operational, and deteriorated after higher doses. The performance of this detector identifies particular risks associated with a p-on-n fine pitch design with a double metal layer.
120004567
Performance of a hydrogen/deuterium polarized gas target in a storage ring
Abstract The performance of a high-density polarized hydrogen/deuterium gas target internal to a medium-energy electron storage ring is presented. Compared to our previous electron scattering experiments with tensor-polarized deuterium at NIKHEF (Zhou et al., Nucl. Instr. and Meth. A 378 (1996) 40; Ferro-Luzzi et al., Phys. Rev. Lett. 77 (1996) 2630; Van den Brand et al., Phys. Rev. Lett. 78 (1997) 1235; Bouwhuis et al., Phys. Rev. Lett. 82 (1999) 687; Zhou et al., Phys. Rev. Lett. 82 (1999) 687) the target figure of merit, ( polarization ) 2 × luminosity , was improved by more than an order of magnitude. The target density was increased by upgrading the flux of nuclear-polarized atoms injected into the storage cell and by using a longer (60 cm ) and colder (∼70 K ) storage cell. A maximal target thickness of 1.2 (1.1)±0.1×10 14 nuclei / cm 2 was achieved with deuterium (hydrogen). With typical beam currents of 110 mA , this corresponds to a luminosity of about 8.4 (7.8)±0.8×10 31 e − nuclei cm −2 s −1 . By reducing the molecular background and using a stronger target guide field, a higher polarization was achieved. The target was used in combination with a 720 MeV polarized electron beam stored in the AmPS ring (NIKHEF) to measure spin observables in electron–proton and electron–deuteron scattering. Scattered electrons were detected in a large acceptance magnetic spectrometer. Ejected hadrons were detected in a single time-of-flight scintillator array. The product of beam and target vector polarization, P e P t , was determined from the known spin-correlation parameters of e ′ p quasi-elastic (or elastic) scattering. With the deuterium (hydrogen) target, values up to P e P t =0.49±0.03 (0.32±0.03) were obtained with an electron beam polarization of P e =0.62±0.04 (0.56±0.03) as measured with a Compton backscattering polarimeter (Passchier et al., Nucl. Instr. and Meth. A 414 (1998) 4988). From this, we deduce a cell-averaged target polarization of P t =0.78±0.07 (0.58±0.07), including the dilution by unpolarized molecules.
118813308
Plans for experiments protection at the LHC
The Large Hadron Collider (LHC), once in operation, will represent approximately a 200-fold increase in stored beam energy with respect to previous high energy colliders. Safe operation will critically rely on machine and experiment protection systems. We describe the general experiment protection strategy against beam failures with some emphasis on silicon vertex detectors of the LHC experiments.
124970019
A polarized 3He internal target for storage rings
A polarized 3He internal target was employed at the internal target facility of the Amsterdam electron Pulse Stretcher and Storage ring (AmPS) at the Dutch National Institute for Nuclear and High-Energy Physics (NIKHEF). The unique features of internal targets such as chemical and isotopic purity, high and rapidly reversible polarization, and the ability to manipulate the target spin orientation were successfully demonstrated. A nuclear polarization of 0.50 (0.42) at a 3He gas #ow of 1.0 (2.0)]1017 at s~1 could be obtained. Operation at a nominal #ow of 1]1017 at s~1 resulted in a target thickness of 0.7]1015 at cm~2 at a target temperature of 17 K. ( 2000 Elsevier Science B.V. All rights reserved.
120334371
Bubble chambers and baryon resonances
56434811
A study of the electron image due to ionizing events in a two-dimensional liquid argon TPC with a 24 cm drift gap
Abstract We have tested a liquid argon time projection chamber with a novel wire configuration based on electrostatic focussing which allows the realization of a nondestructive detection of the electron image produced by ionizing events. The chamber was tested in a 5 GeV pion beam at the CERN proton synchrotron. The measured pulse shapes at both 200 V/cm and 500 V/cm were in very good agreement with the expected shapes, calculated taking into account the electron lifetime, the response of the electronics and the longitudinal diffusion of the electron cloud. The measured electron drift velocity was in good agreement with the results of other workers as well as with our previous measurements. We have also analysed a sample of events containing delta rays in order to study the behaviour of low-energy electrons in the liquid argon. We find that for electron energies greater than 5 MeV the measured energy spectrum agrees very well with the predicted spectrum after corrections for acceptance and energy loss, hence demonstrating the feasibility of recognizing low-energy electrons in liquid argon.