E. E. Schmidt

Magnetic Field Properties of Fermilab Energy Saver Dipoles

At Fermilab we have operated a production line for the fabrication of 901 21 foot long superconducting dipoles for use in the Energy Saver/Doubler. At any one time 772 of these dipoles are installed in the accelerator and 62 in beamlines; the remainder are spares. Magnetic field data are now available for most of these dipoles; in this paper we present some of these data which show that we have been able to maintain the necessary consistency in field quality throughout the production process. Specifically we report harmonic field coefficients, showing that the mechanical design permits substantial reduction of the magnitudes of the normal and skew quadrupole harmonic coefficients; field shape profiles; integral field data; and field angle data. Details of the measurement apparatus and procedures are described elsewhere.

Report on the Production Magnet Measurement System for the Fermilab Energy Saver Superconducting Dipoles and Quadrupoles

The measurement system and procedures used to test more than 900 superconducting dipole magnets and more than 275 superconducting quadrupole magnets for the Fermilab Energy Saver are described. The system is designed to measure nearly all parameters relevant to the use of the magnets in the accelerator including maximum field capability and precision field measurements. The performance of the instrumentation with regard to precision, reliability, and operational needs for high volume testing will be described. Previous reports have described the measurement system used during development of the Saver magnets from which this system has evolved.

Magnetic Field Data on Fermilab Energy Saver Quadrupoles

The Fermilab Energy Saver/Doubler (Tevatron) accelerator contains 216 superconducting quadrupole magnets. Before installation in the Tevatron ring, these magnets plus an additional number of spares were extensively tested at the Fermilab Magnet Test Facility (MTF). Details on the results of the tests are presented here.

Application of NMR Circuit for Superconducting Magnet Using Signal Averaging

An NMR circuit was used to measure the absolute field values of Fermilab Energy Doubler magnets up to 44 kG. A signal averaging method to improve the S/N ratio was implemented by means of a Textronix Digital Processing Oscilloscope, followed by the development of an inexpensive microprocessor based system contained in a NIM module. Some of the data obtained from measuring two superconducting dipole magnets is presented.

Experimental evaluation of design features of a cryostat for an iron-less COSθ- SSC magnet

A conceptual design for an iron-less cosθ SSC magnet cryostat has identified several areas for experimental study. Included are bowing of thermal radiation shields due to cooldown and warmup; thermal performance of the suspension systems; cryostat thermal performance; structural responses to decentering forces between the coil and the steel vacuum vessel; and response of thermal shields to forces due to quench induced eddy currents. Studies were carried out with 6m long thermal bowing and magnetic effects models, a suspension heat leak measurement dewar and a 12m long thermal model. The models incorporate important features of the conceptual cryostat design. The details of the test arrangements, procedures and results are presented.

The CDF II 3D-Track Level 2 Trigger Upgrade

The CDF II level 1 track trigger system reconstructs charged tracks in the plane transverse to the beam direction. The track trigger electronics uses the hit data from the 4 axial layers of the CDF II central outer tracking chamber, and has been recently upgraded to include the complementary information from the 3 stereo layers. Together with the existing system it provides improved fake track rejection at level 1. In addition, the high resolution segment information is delivered to the Level 2 processors, where software algorithms perform three-dimensional stereo track reconstruction. The 3D-tracks are further extrapolated to the electromagnetic calorimeter towers and muon chambers to generate trigger electron and muon candidates. The invariant mass of track pairs and track isolations are also calculated and used in the level 2 trigger decision. We describe the hardware and software for the level 2 part of the track trigger upgrade as well as the performance of the new track trigger algorithms.

The CDF II Level 1 Track Trigger Upgrade

The CDF II detector uses dedicated hardware to identify charged tracks that are used in an important class of level 1 trigger decisions. Until now, this hardware identified track segments based on patterns of hits on only the axial sense wires in the tracking chamber and determined the transverse momentum of track candidates from patterns of track segments. This identification is efficient but produces trigger rates that grow rapidly with increasing instantaneous luminosity. High trigger rates are a consequence of the large numbers of low momentum tracks produced in inelastic collisions which generate overlapping patterns of hits that match those expected for high-momentum tracks. A recently completed upgrade to the level 1 track trigger system makes use of information from stereo wires in the tracking chamber to reduce the rate of false triggers while maintaining high efficiency for real high momentum particles. We describe the new electronics used to instrument the additional sense wires, identify track segments and correlate these with the track candidates found by the original track trigger system. The performance of this system is characterized in terms of the efficiency for identifying charged particles and the improved rejection of axial track candidates that do not correspond to real particles.

5-cm, No Iron SSC 6-m Dipole Test Program

Magnet Design B for the Superconducting Super Collider (SSC) consists of a 5 cm diameter collared coil assembly 12 m long with concentric aluminum thermal shields at 10 K and 80 K, a G-10 post type support system and a minimal iron vacuum vessel located at a large radius from the coil. In order to determine the behavior of such a magnet under both direct current and quenching conditions, a 6 m model was built using Tevatron tooling to produce a 7.6 cm diameter coil. The dc operation demonstrated that the post type suspension has acceptable rigidity. Distortions in the aluminum thermal shield during quench resulted from stresses in the material below the yield values. Temperature increases in the thermal shield due to eddy currents were larger than those calculated using simple assumptions, demonstrating the value of using a model to verify eddy current behavior in complex situations.

The ironless cos θ magnet option for the SSC

The Fermilab design of a 5 T, 5 cm aperture superconducting dipole is described, that attempts to integrate essential cryogenic details with a low cold mass, low heat leak magnet containing a coil surrounded by aluminum collars. Operating characteristics of coils made with aluminum collars are presented along with harmonic data obtained from 1 meter long 5 cm aperture collared coils. A summary of results obtained from cold tests of a 7.6 cm aperture, 6 m long aluminum collared coil in an iron vacuum vessel cryostat are reviewed. Results from the measurement of heat leak to 4.5K, 10K, and 80K are discussed for a 12 m prototype cryostat. Calculations are summarized for passively correcting the persistent current sextupole fields.