R. Hamatsu

TEST OF THE ZEUS FORWARD CALORIMETER PROTOTYPE

Abstract Four prototype modules following the same design as the ZEUS forward calorimeter (FCAL) modules have been constructed and tested with electrons, hadrons and muons in the momentum range of 1 to 100 GeV/ c . The main topics under investigation were: calibration, uniformity of response, noise, light yield, energy resolution and the electron to hadron response (e/h ratio). The result of the measurements is presented and the expected performance of the FCAL is discussed in the light of these results.

Response of a uranium-scintillator calorimeter to electrons, pions and protons in the momentum range 0.5–10 GeV/c

Abstract We have exposed a sandwich calorimeter, consisting of 3.3 mm thick uranium pnterleaved with 2.6 mm thick scintillator tiles, to positive and negative electrons and pions and to protons in the momentum range of 0.5 to 10 GeV/c. We find that e/h is about 1 above 3 GeV/c, but decreases significantly for lower momenta. This ratio is the same for positive and negative pions and also for pions and protons of the same kinetic energy.

Feasibility of optical diffraction radiation for a non-invasive low-emittance beam diagnostics

Abstract A “proof-of-principle” experiment on the optical diffraction radiation (ODR) as a single-pulse beam profile monitor is planned using an electron beam extracted from the KEK-ATF damping ring. The main goals of this experiment are the following: (i) To measure the yield and the angular distributions of the optical diffraction radiation from a large-size target at different wavelengths, impact parameters and beam characteristics for a comparison with analogous characteristics of optical transition radiation from a foil with identical optical parameters and for a verification of the model assumption (perfectly conducting semi-infinite target). (ii) To investigate the ODR angular distributions from a tilted target with a slit for observing the interference effects. (iii) To compare the results obtained by simulations based on classical approaches, taking into account the optical characteristics of the equipment and the beam parameters. (iv) To estimate the prospects of using ODR as a new non-invasive tool for ultrarelativistic beams. We estimated that the ODR photon yield in 10% bandwidth for 500 nm is about 106 photons/bunch with an impact parameter of 100 μm . This indicates that the ODR monitor is a promising candidate for single-pulse beam-profile measurements, and that it will be an extremely useful instrument for future linear colliders (JLC, NLC, TESLA and CLIC).

A modular straw drift tube tracking system for the Solenoidal Detector Collaboration experiment Part I. Design

Abstract We have developed the baseline design for a straw drift tube tracking system for the Solenoidal Detector Collaboration (SDC) detector. The system was designed to operate in the high-rate environment of a high luminosity hadron collider. We present an overview of the tracking system and the requirements it was expected to fulfill. We describe the construction and properties of the straw drift tubes. We discuss the design of the carbon-fiber foam-laminate shell, which supported the wire tension and held the straws in alignment. We also present descriptions of the designs of the front-end and digitization electronics as well as the electronics associated with the level 1 track trigger.

Experimental study of positron production from a W single crystal by the KEK 8-GeV electron linac beam

Abstract We have measured the positron production efficiency from tungsten single-crystal targets using an 8 GeV electron beam. A single-bunch beam with a bunch width of 10 ps, a repetition rate of 2 Hz, and an intensity of 0.2 nC/bunch was incident on a target mounted on a precision goniometer. Positrons produced in the forward direction were detected by a magnetic spectrometer in the 10–20 MeV/c momentum range. Systematic data on the target-thickness dependence and the momentum distribution of the produced positrons were obtained for crystal targets. The results show that, when the crystal axis 〈1 1 1〉 is aligned to the electron beam direction, the positron yield increases compared to the amorphous case by factors of 6.5, 3.4 and 2.3 at 10 MeV/c for 2.2, 5.3 and 9.0 mm thick crystals, respectively. We observed that the positron yield from the 9.0 mm thick crystal is larger than the maximum yield attainable with 18–20 mm thick amorphous targets at 8 GeV.

Status of optical diffraction radiation experiment at KEK-ATF extraction line

Abstract At KEK-ATF extraction line detailed investigation of backward optical diffraction radiation (ODR) and its implementation to transversal beam parameter diagnostics is planned. We designed and constructed a target chamber with a precise target movement mechanism, a precise laser alignment system and an optical system. The first step to achieve success in the experiment is the tuning of the optical system using backward optical transition radiation (OTR). We believe that, if we are able to measure OTR spectral-angular characteristics with a proper accuracy, we may obtain good results for ODR measurements as the OTR effect is well experimentally and theoretically studied. Therefore, the first stage of our experiment assumes the measurements of backward OTR to analyze all possible types of radiation coming from the target, which could be obstacles for the ODR measurements. In the first series of experiments we have found that the angular distribution of the detected optical radiation is strongly asymmetric. One of the possible reasons for the asymmetry is the synchrotron radiation contribution from bending or steering magnets.

Grating optical diffraction radiation – Promising technique for non-invasive beam diagnostics

Abstract Two simple approaches for evaluating the transversal beam size using a slit and a grating are presented. A model for calculating the resonant diffraction radiation (RDR) characteristics from grating consisting of perfectly conducting strips spaced by vacuum gaps is developed. The proposed model allows calculating the RDR characteristics for a beam passing through a big slit between two gratings. It is noted that quasimonochromatic maxima appear in the RDR spectral–angular distribution, whose position is determined by the grating’s period and observation geometry. The peak shape depends on the beam parameters. Having measured the RDR angular distribution at a fixed wavelength, one may evaluate the beam size using simple formulas obtained.

SIMULATION STUDIES OF TRACKING SYSTEMS AT VERY HIGH LUMINOSITY

Abstract Detailed computer simulation studies of a tracking detector originally designed for high luminosity operation at the Superconducting Super Collider have been carried out. Detector simulation and track reconstruction techniques appropriate to the extremely high charged particle rates corresponding to luminosities of up to 10 34 cm −2 s −1 are described. The detector performance is evaluated and compared to design requirements stemming from the physics goals of the SDC experiment. The results have implications for the design of tracking detectors at future high luminosity hadron colliders such as the Large Hadron Collider (LHC).

Enhancement of the positron intensity by a tungsten single-crystal target at the KEKB injector linac

A new tungsten single-crystal target has been successfully employed at the positron source of the KEKB injector linac. The crystal thickness was determined to be 10.5 mm based on the previous systematic measurements of the positron-production efficiency. The crystal axis, lang111rang, was precisely aligned to the direction of the 4-GeV primary electron beam. The positron yield increased by ~25% compared to that for a conventional tungsten plate with a thickness of 14 mm. On the contrary, the heat load on the crystal target decreased by ~20%. No degradation of the positron-production efficiency was observed since the crystal target was installed in September 2006, and it has been stably operating at the KEK B-factory.

Beam Test Proposal of an ODR Beam Size Monitor at SLAC FFTB

ODR(Optical Diffraction Radiation) transverse beam size measurement at the SLAC FFTB at 28.5 GeV is a challenge and it requires special target and optics system, which is much difficult than the conventional ODR beam size measurement. We propose to use a curved disphased conductive slit target to recover the sensitivity in the measurement of the single bunch transverse beam size by using ODR photons from a conductive slit. In order to cancel the effect of the beam divergence, the conductive slit target surface must be curved. Also, we can obtain the focused interference pattern of the ODR photons at the detector at the shorter distance from the target than the γ2λ, by using lens optics system.