J. Crittenden

Construction and beam test of the ZEUS forward and rear calorimeter

Abstract The forward and rear calorimeters of the ZEUS experiment are made of 48 modules with maximum active dimensions of 4.6 m height, 0.2 m width, 7 λ depth and maximum weight of 12 t. It consists of 1 X 0 uranium plates interleaved with plastic scintillator tiles read out via wavelength shifters and photomultipliers. The mechanical construction, the achieved tolerances as well as the optical and electronics readout are described. Ten of these modules have been tested with electrons, hadrons and muons in the momentum range 15–100 GeV/ c . Results on resolution, uniformity and calibration are presented. Our main result is the achieved calibration accuracy of about 1% obtained by using the signal from the uranium radioactivity.

A measurement of σtot (γp) at √s=210 GeV

Abstract The total photoproduction cross section is determined from a measurement of electroproduction with the ZEUS detector at HERA. The Q 2 values of the virtual photons are in the range 10 −7 Q 2 −2 GeV 2 . The γp total cross section in the γp centre of mass energy range 186–233 GeV is 154 ± 16 (stat.) ± 32 (syst.) μ b.

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.

Design considerations for the CESR-c wiggler magnets

The damping-dominated beam dynamics of the CESR storage ring modified to operate in the 1.5-3 GeV energy range impose unique and stringent design specifications on the 1.3-m-long superconducting wiggler magnets which provide the necessary damping. A superferric 7-pole wiggler magnet which meets these design specifications has been designed, built and tested in situ. Studies of finite-element models and particle-tracking simulations have shown that that an 8-pole model of similar design will provide improved consistency in transfer functions when operated at peak fields which differ from the primary design value.

A magnetic field model for wigglers and undulators

Recent interest in applications of wiggler magnets in storage rings has motivated efforts to incorporate their effects in calculations of beam dynamics. This paper presents an analytic model of wiggler fields that can be used with symplectic integration to evaluate such effects. Coefficients needed by the model are generated by fitting to the results of a finite-element field calculation. The model has been used successfully in the CESR-c project, which imposes tolerances of a few parts in 10/sup 4/ on the modeling of 2-Tesla superconducting wigglers. In contrast to models based on Fourier transforms, the model presented here uses a relatively small number of terms, leading to correspondingly fast integration times. Fringe fields are included and no assumption about the periodicity of the field is made.

Electron Cloud Buildup Characterization Using Shielded Pickup Measurements and Custom Modeling Code at CESRTA

The Cornell Electron Storage Ring Test Accelerator experimental program includes investigations into electron cloud buildup, applying various mitigation techniques in custom vacuum chambers. Among these are two 1.1-m-long sections located symmetrically in the east and west arc regions. These chambers are equipped with pickup detectors shielded against the direct beam-induced signal. They detect cloud electrons migrating through an 18-mm-diameter pattern of small holes in the top of the chamber. A digitizing oscilloscope is used to record the signals, providing time-resolved information on cloud development. Carbon-coated, TiN-coated and uncoated aluminum chambers have been tested. Electron and positron beams of 2.1, 4.0 and 5.3 GeV with a variety of bunch populations and spacings in steps of 4 and 14 ns have been used. Here we report on results from the ECLOUD modeling code which highlight the sensitivity of these measurements to the physical phenomena determining cloud buildup such as the photoelectron production azimuthal and energy distributions, and the secondary yield parameters including the true secondary, re-diffused, and elastic yield values.

Measurement of electron trapping in the Cornell Electron Storage Ring

The buildup of low-energy electrons has been shown to affect the performance of a wide variety of particle accelerators. Of particular concern is the persistence of the cloud between beam bunch passages, which can impose limitations on the stability of operation at high beam current. We have obtained measurements of long-lived electron clouds trapped in the field of a quadrupole magnet in a positron storage ring, with lifetimes much longer than the revolution period. Based on modeling, we estimate that about 7% of the electrons in the cloud generated by a 20-bunch train of 5.3 GeV positrons with 16-ns spacing and

Field Modeling for the CESR-C Superconducting Wiggler Magnets

1.3x10^{11}

Beam based characterization of a new 7-pole superconducting wiggler at CESR

population survive longer than 2.3