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Microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments1 have been used to investigate the mechanism of RF breakdown.2 The images show evidence for melting and boiling in small regions of ~10 micron diameter on tungsten, molybdenum, and beryllium electrode surfaces. In these experiments, the dense hydrogen gas in the cavity prevents electrons or ions from being accelerated to high enough energy to participate in the breakdown process so that the only important variables are the fields and the metallic surfaces. The distributions of breakdown remnants on the electrode surfaces are compared to the maximum surface gradient E predicted by an ANSYS model of the cavity. The local surface density of spark remnants, proportional to the probability of breakdown, shows a strong exponential dependence on the maximum gradient, which is reminiscent of Fowler-Nordheim behavior of electron emission from a cold cathode. New simulation results have shown good agreement with the breakdown behavior of the hydrogen gas in the Paschen region and have suggested improved behavior with the addition of trace dopants such as SF 6.3 Present efforts are to extend the computer model to include electrode breakdown phenomena and to use scanning tunneling microscopy to search for work function differences between the conditioned and unconditioned parts of the electrodes.

Eighteen 5-cm-aperture, 15-m-long Superconducting Super Collider (SSC) dipole magnet prototypes have been produced and cold tested. On each prototype, the dependence of harmonic field coefficients on magnetic current was measured as part of a study of the magnetic field quality. For most of the magnets, the observed behavior conforms to what can be expected from the effects of persistent magnetization currents and iron yoke saturation. A few prototypes, however, exhibited anomalies during current ramp at 4 A/s which can be attributed to large cable eddy currents. >

Tests have recently been performed at Fermilab in order to measure the energy losses due to eddy currents and iron and superconductor magnetization. These measurements were performed on six 1.5-m-long model magnets and eight 15-m-long full-scale collider dipole magnets. AC losses were measured as a function of ramp rate using sawtooth ramps from 500 to 5000 A for both types of magnets, while bipolar studies were additionally performed on some of the short magnets. The measured magnet voltage and current for a complete cycle were digitally integrated to yield the energy loss per cycle. Measurement reproducibility was typically 5%, with good agreement between long magnet measurements and extrapolations from short magnet measurement results. Magnetization loss measurements among similar magnet types agree to within experimental error, while eddy current losses correlate strongly with the observed dependence of quench current on ramp rate. >

The quench performance and ramp rate sensitivity of 18 5-cm-aperture, 15-m-long Superconducting Super Collider (SSC) dipole magnet prototypes are discussed. All the magnets appear to reach a quench plateau near their extrapolated short sample current limit and well in excess of the operating current with very little training. Most of the magnets, however, exhibit a dramatic degradation of their quench current as a function of ramp rate, which, for the most part, can be attributed to large cable eddy currents. >

Several 40-mm-aperture, 17-m-long dipoles have been built by Fermilab as developmental prototypes for the Superconducting Super Collider (SSC). These magnets have an external inner-outer coil splice design, a collet style end clamp assembly, a new, analytically designed minimum stress coil end design, and a new insulation system which does not employ shims or 'shoes'. In addition, the magnets were built using production-style tooling. The magnets were tested at the Fermilab Magnet Testing Facility. Quench testing and mechanical measurement results are presented and analyzed with emphasis on the new design and fabrication features of these magnets. The performance of these magnets was very good from a quench and mechanical behavior standpoint. The magnets did not exhibit excessive training behavior and only one training quench was below the nominal operating current. The coil prestress remained positive to >7 T in both magnets and most of the quenches originated in the high field region of the pole turn. >

Magnetic field measurements have been made on twelve 17-m-long, 40-mm-aperture R&D superconducting dipoles. Data on dipole field strength, multipole coefficients, and alignment have been obtained. The data indicate that the magnets as built are generally within the expectations for this design. >

Eleven 17-m-long, 40-mm-aperture SSC (Superconducting Super Collider) R&D superconducting collider dipole magnets, built at BNL (Brookhaven National Laboratory), have been extensively tested at BNL and Fermilab during 1990-1. Quench performance of these magnets and details of their mechanical behavior are presented. Although the quench performance of the most recent magnets shows slightly more quenches than expected, there is now a better understanding of the mechanical behavior of these magnets. The baseline design leads to reasonable quench performance. The quench performance of the DC series magnets seems to indicate a strong sensitivity to change in design parameters, key among them being the collar-yoke interference and the coil end loading. >

Most ionization cooling schemes now under consideration are based on using many large flasks of liquid hydrogen energy absorber. One important example is the proposed Muon Ionization Cooling Experiment (MICE), which has recently been approved to run at the Rutherford Appleton Laboratory (RAL). In the work reported here, a potential muon cooling demonstration experiment based on a continuous liquid energy absorber in a helical cooling channel (HCC) is discussed. The original HCC used a gaseous energy absorber for the engineering advantage of combining the energy absorption and RF energy regeneration in hydrogen-filled RF cavities. In the Muon And Neutrino eXperiment (MANX) that is proposed here, a liquid-filled HCC is used without RF energy regeneration to achieve the largest possible cooling rate in six dimensions. In this case, the magnetic fields of the HCC must diminish as the muons lose momentum as they pass through the liquid energy absorber. The length of the MANX device is determined by the maximum momentum of the muon test beam and the maximum practical field that can be sustained at the magnet coils. We have studied a 3 meter-long HCC example that could be inserted between the MICE spectrometers at RAL.

Ionization cooling, a method for shrinking the size of a muon beam, requires a low Z energy absorber, high field magnets, and high gradient radio frequency cavities. The use of high temperature superconductors (HTS) for the high field superconducting magnets is being considered to realize a helical muon cooling channel using hydrogen refrigeration. A test stand was set up at Fermilab to perform critical current (Ic) measurements of HTS wires under externally applied perpendicular and parallel fields at various temperatures. A description of the test setup and results on (Bi,Pb)2Sr2Ca2Cu3Ox (BSCCO‐2223) tapes and Bi2Sr2CaCu2O8 (BSCCO‐2212) round wires are presented. Finally, the engineering critical current density, JE, of HTS and Nb3Sn were compared in the application’s field and temperature range of interest.

Four full-scale SSC (Superconducting Super Collider) development dipole magnets have been tested for mechanical and quench behavior. Two are of a design similar to that of previous magnets but contain a number of improvements, including more uniform coil size, higher prestress, and a redesigned inner-outer coil splice. One exceeds the SSC operating current on the second quench, but the other appears to be limited by damaged superconductor to a lower current. The other two magnets are of alternate designs. One trains erratically and fails to reach a plateau, and the other reaches a plateau after four quenches. >

Ionization cooling, a method for shrinking the size of a particle beam, is an essential technique for future particle accelerators that use muons. In this technique, muons lose energy in all three directions by passing through an absorber while only the longitudinal energy is regenerated by RF cavities. Thus the beam phase space area decreases down to the limit of multiple scattering in the energy absorber. Hydrogen is the material of choice for ionization cooling because of its long radiation length relative to its energy loss. In the application discussed here, dense gaseous hydrogen also suppresses RF breakdown by virtue of the Paschen effect, thereby allowing higher accelerating gradients and a shorter and less‐expensive cooling channel. As described in this paper, a channel of RF cavities pressurized with about 3 tons of cold hydrogen gas could provide transverse muon cooling for a Muon Collider or Neutrino Factory. The present status of this research effort and several issues related to the use of hydrogen in this application are described.

In order to increase the usable accelerating gradient in Superconducting TESLA cavities, the field emission threshold barrier must be raised. As has been previously demonstrated on S-Band cavities, a way to accomplish this is with the use of high peak power RF processing. A transmitter with a peak power of 2 MWatt and 300 /spl mu/sec pulse length has been assembled and has been used to process TESLA cavities. Several five cell TESLA cavities at 1.3 GHz have been manufactured for this purpose. This transmitter and the cavities will be described and the results of the tests will be presented. >

A research and development program is underway to construct superconducting cavities to be used for radiofrequency separation of a kaon beam at Fermilab. The design calls for installation of twelve 13-cell cavities operating in the 3.9 GHz transverse mode with a deflection gradient of 5 MV/m. We present the mechanical, cryogenic and vacuum design of the cavity, cryomodule, rf power coupler, cold tuner and supporting hardware. The electromagnetic design of the cavity is presented in a companion paper by Wanzenberg and McAshan (2001). The warm tuning system (for field flatness) and the vertical test system will be presented along with test results of bench measurements and cold tests on single-cell and five-cell prototypes.

The facility at Fermilab was used to develop, fabricate, and commission an RF gun for the TeSLA Test Facility Linac. A time dependence is observed in the photo-emission and field emission from the photo-injector at Fermilab. The focussing solenoids can be adjusted to cause the QE and dark current to increase or decrease with time. The observed variation is in excess of a factor of 5 in the QE and a factor of 10 in the dark current, with time constants measured in hours. The evidence suggests that the source of the time-dependent behaviour is the Cs/sub 2/Te cathode.

Measurements of the magnetic field angle along the length of collider dipole magnets are discussed. These superconducting magnets were built at Fermilab for the Superconducting Super Collider (SSC) by Fermilab and General Dynamics personnel. These measurements were made at four stages in the assembly and test sequence. The data show that changes can occur both during installation in the cryostat and as a result of cold testing. Most of the changes during installation are correlated with the welding of the tie bar restraints, but the changes observed as a result of the cold testing can be attributed to changes in the magnetization of the iron laminations. >

An electron photo-injector facility has been constructed at Fermilab for the purpose of providing a 14-18 MeV electron beam with high charge per bunch (8 nC), short bunch length (1 mm RMS), and small transverse emittance. The facility was used to commission a second-generation photo-cathode RF gun for the TESLA Test Facility (TTF) Linac at DESY; in the future, the Fermilab electron beam will be used for R and D in bunch length compression, beam diagnostics, and new acceleration techniques. Acceleration beyond 4 MeV is provided by a 9-cell superconducting cavity. The cavity also provides a longitudinal position-momentum correlation for subsequent bunch length compression. We report on the RF tests and a first beam test of this cavity.

An RF photo-injector was installed at Fermilab between January and June 97. The photo-injector produced its first beam on 4 June 97. This report provides a brief description of the accelerator and a summary of the experiments carried out through December '97.

A collaboration has been formed between FNAL, UCLA, LNFN Milano, the University of Rochester, and DESY to develop the technology of an RF photoinjector, followed by a superconducting cavity, to produce high bunch charge (8 nC) with low normalized emittance (

The electrical resistance of superconducting cable splices is known to be in the 10{sup -9} {Omega} range which to be measured conventionally would require the use of a micro voltmeter with a power supply capable of generating kilo Amperes plus a liquid helium cryostat with large power leads. Here we present a system for carrying on such measurements that requires besides the microvoltmeter a power supply capable of generating only up to 35 {Alpha} and a 152 mm diameter neck helium dewar using less than 25 liters per day after initial cool down. In this paper we describe the apparatus and present the data taken with it in its first use which for data acquisition used just a chart recorder. The method is based in making the splice in a loop of cable, inducing a current in it and measuring its decay time constant. Generating high currents in superconductors by induction is not a new technique but the use of the decay constant of currents generated this way for the determination of minute electrical resistance seems novel to the author. Unexpected details in the results will be discussed.

Similar to the power leads of accelerator superconducting magnets, the power couplers of accelerator superconducting cavities are components that link room temperature to superfluid helium temperature for the purpose of energy transfer. Instead of conducting kiloamperes of current they guide megawatts of RF power between those two temperatures. In this paper we describe a cryostat designed for testing the performance of these components and measuring their heat loads. A special feature of this cryostat is its minimum liquid inventory that considerably simplifies safety related requirements. This cryostat is part of a Fermilab facility contributing to the international collaboration working on TESLA (TeV Electron Superconducting Linear Accelerator). This facility is now operational and we will be presenting specifications as well as performance data on the cryostat as well as the first pair of power couplers tested with it.

A facility for coating RF power components with thin films of Ti and/or TiN has been in operation for some time at Fermilab supporting the Accelerator Division RF development work and the TESLA program. It has been experimentally verified that such coatings improve the performance of these components as far as withstanding higher electric fields. This is attributed to a reduction in the secondary electron emission coefficient of the surfaces when coated with a thin film containing titanium. The purpose of this Technical Memorandum is to describe the facility and the procedure used.

During 1992 at Fermilab, a series of nine 50-mm-aperture, 15-m-long, SSC superconducting dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, and the SSC Laboratory, have been built and successfully cold tested. Seven of these dipole magnets, designated for the Accelerator System String Test (ASST) carried out at SSCL in Dallas, were assembled at Fermilab by General Dynamics personnel, and have achieved the nominal operating current level without significant training.1,2 In addition, a series of four R&D magnets (DCA320 323) were manufactured at Fermilab to test an alternative insulation schemes. In this paper we present the quench performance of these four R&D magnets, which were cold tested at the Fermilab Magnet Test Facility at nominal temperatures of 4.35 K, 3.85 K, and 3.50 K. An extended characterization test was performed on one of these magnets (DCA322). During this test the magnet was successfully cooled down to superfluid He temperature (1.8 K) and reached a field B ≥ 9.5 T.

At several stages in the production of the SSC collider dipole magnets and their final installation (as well as for beam orbit calculations) the magnetic field angle needs to be known. A simple device using a permanent magnet which aligns itself with the magnetic field (the Vertical Field Angle Probe, FAP) had been developed at FNAL to survey the direction of the magnetic dipole field with respect to the vertical (as determined by gravity) along the magnet axis.1 The determination of the dipole field angle was part of the field quality characterization of a series of thirteen full-length 50mm-aperture SSC Collider Dipole Magnet Prototypes (DCA311-DCA323) which were built for R&D purposes at FNAL (for design specification).5,6

Experiences are reported of welding niobium to stainless steel for the TESLA accelerator superconducting cavities.

Thirteen 16 m long, 50 mm aperture SSC dipole magnets, designed jointly by Fermilab, Brookhaven National Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory, have been built at Fermilab. The first nine magnets have been fully tested to date. The allowed harmonics are systematically shifted from zero by amounts larger than the specification. The unallowed harmonics, with the exception of the skew sextupole, are consistent with zero. The magnet-to-magnet RMS variation of all harmonics is much smaller than the specification.

In the fabrication of both 40 and 50 mm collider dipole superconducting magnets, surveys of the direction of the magnetic field along their length have been taken. This data besides being used for certifying compliance with the specifications for the finished magnet, yields interesting information on the straightness and rigidity of the coil placement between some stages in their manufacture and testing. A discussion on the measuring equipment and procedures is given. All of the 40 mm magnets that were built or cryostat at Fermilab have at least one of these surveys, and a summary of the data on them is presented. Most of the 50 mm magnets built and cold tested at Fermilab have been surveyed before and after insertion in the cryostat and before and after being cold tested. A summary of this data is also presented.

This note is about calculations aimed at quantifying adequate pumping speeds of evacuation of normally humid clean-room air from typical Superconducting Radiofrequency (SRF) cavities. The subject is of high relevance to the semiconductor industry, where the yield of VLSI (Very Large Scale Integration) chip production is affected by micron size particles which may cause fatal defects to their micron and sub-micron features. The recent availability of particle counters capable of operating in vacuum has stimulated measurements at reduced pressures in this subject.

This paper presents preliminary results of magnetic field measurements made on a series of 50 mm aperture 15 m long SSC collider dipole magnets designed and manufactured at Fermi National Accelerator Laboratory (Fermilab) for use in the Superconducting Super Collider Laboratory (SSCL) Accelerator System String Test. The magnets were assembled by Fermilab and General Dynamics personnel, and were tested at the Magnet Test Facility (MTF) at Fermilab. Measurements of the dipole field angle, dipole field strength, and field shape parameters at various stages in magnet construction and testing are described.

In this paper we present results of quench testing of full length SSC dipole magnets at Fermilab. The data are from the first six of a series of thirteen 15 m long, 50 mm aperture SSC dipole magnets which are being built and tested at Fermilab. These magnets were designed jointly by Fermilab, Brookhaven Laboratory, Lawrence Berkeley Laboratory and the SSC Laboratory. Among the major goals for this series of magnets are to transfer magnet production technology to the lead vendor for the Collider Dipole Magnet, the General Dynamics Corporation, and to demonstrate industrial production by the vendor. The first magnet in the series, DCA311, was built by Fermilab technicians to establish assembly procedures. The second magnet, DCA312, was the “technology transfer magnet and was built jointly by Fermilab and General Dynamics technicians. The next seven, DCA313-319 are being built by General Dynamics personnel using Fermilab facilities and procedures. However, Fermilab personnel still operate the major tooling, provide the welders, perform assembly of items that would not be part of production magnets (e.g. voltage taps), and oversee the QA program. Five of these 7 GD-built magnets will be used in the Accelerator Systems String Test (ASST) to be carried out in Dallas later this year. The last four magnets, DCA320-323, are being built by Fermilab alone.”

A series of full-scale demonstration SSC collider dipole magnets were built for the ASST (Accelerator System String Test). These magnets, DCA311 through DCA319, have 50 mm aperture and 15 m magnetic length with 6.6 Tesla uniform field. For the support structure of the W6733B cross section[1], the Fermilab design uses a vertical split[2] in the yoke. The end sections of the magnet have solid spacers and are supported by collet clamps[3]. The splices between inner and outer coils are made in preforms which lie outside of the high field region. The magnets were produced in pipeline fashion with no intentional major changes between magnets. As a part of the technology transfer program, the last 7 magnets were built by General Dynamics personnel using the magnet construction facilities of Fermilab, while the first two magnets were built entirely by Fermilab personnel.

During the last two years, nine 4‐cm aperture, 17‐m‐long dipole magnet prototypes were produced by Brookhaven National Laboratory (BNL) under contact with the Superconducting Super Collider (SSC) Laboratory. These prototypes are the last phase of a half‐decade‐long R&D program, carried out in collaboration with Fermi National Accelerator Laboratory and Lawrence Berkeley Laboratory, and aimed at demonstrating the feasibility of the SSC main‐ring dipole magnets. They also lay the groundwork for the 5‐cm‐aperture dipole magnet program now underway. After reviewing the design features of the BNL 4‐cm‐aperture, 17‐m‐long dipole magnets, we describe in detail the various steps of their fabrication. For each step, we discuss the paramaters that need to be mastered, and we compare the values that were achieved for the nine most recent prototypes. The data appear coherent and reproducible, demonstrating that the assembly process is under control. We then analyze the mechanical behavior of these magnets during cooldown and excitation, and we attempt to relate this behavior to the magnet features. The data reveal that the mechanical behavior is sensitive to the collar‐yoke interference and that the magnets exhibit somewhat erratic changes in coil end‐loading during cooldown.

The construction and performance of an electric current meter that operates in liquid He and mechanically splits apart to permit replacement of the current carrying conductor is described. It permits the measurement of currents induced in a loop of superconducting cable and expeditious exchange of such loops. It is a key component for a short sample cable testing facility that requires no high current power supplies nor high current leads. Its superconducting pickup circuit involves a non-magnetic core toroidal split-coil that surrounds the conductor and a solenoid whose field is sensed by a Hall probe. This toroidal split-coil is potted inside another compensating toroidal split-coil. The C shaped half toroids can be separated and brought precisely together from outside the cryostat. The Hall probe is energized and sensed by a lock-in amplifier whose output drives a bipolar power supply which feeds the compensating coil. The output is the voltage across a resistor in this feedback circuit. Currents of up to 10 kA can be measured with a precision of 150 mA. 3 refs., 4 figs.

The procedure for installing Superconducting Super Collider dipoles in their respective cryostats involves aligning the average direction of their field with the vertical to an accuracy of 0.5 mrad. The equipment developed for carrying out these measurements is described and the measurements performed on the first few prototype magnets are presented. The field angle as a function of position in these 16.6-m long magnets is a characteristic of the individual magnet with possible feedback information to its manufacturing procedure. A comparison of this vertical alignment characteristic with a magnetic-field intensity (using magnetic resonance imaging) characteristic for one of the prototypes is also presented. >

The experimental study leading to the determination of the sensitivity needed for protecting the Fermilab Doubler from damage during quenches is presented. The quench voltage thresholds involved were obtained from measurements made on Doubler cable of resistance × temperature and voltage × time during quenches under several currents and from data collected during operation of the Doubler Quench Protection System as implemented in the B-12 string of 20 magnets. At 4kA, a quench voltage threshold in excess of 5.0V will limit the peak Doubler cable temperature to 452K for quenches originating in the magnet coils whereas a threshold of 0.5V is required for quenches originating outside of coils.

During the last few months, several full size prototype dipole magnets for the Fermilab Energy Doubler were successfully tested. This was the result of several concurrent programs in conductor development as well as magnet construction, production, and testing. The present magnets have achieved their design goal. Progress to this point has solved many pitfalls. A description is given of the present technology as well as some of the decisions that led to the present design.

Four full-scale SSC (Superconducting Super Collider) research and development dipole magnets, incorporating successive mechanical design improvements, have been quench-tested. Three of the magnets are heavily instrumented with sensors to measure their mechanical behavior and verify the effectiveness of the mechanical improvements and with multiple voltage taps to locate the origin of quenches. The last two magnets of this series reach the SSC design operating field of 6.6 T in two or fewer quenches. Load cells and motion sensors show that in these two magnets the azimuthal clamping stress is higher at zero current and drops more slowly with excitation that in previous long magnets, and that the axial motion of the coil upon excitation has been greatly reduced. Quenches are found to originate preferentially in several locations, suggesting other design improvements. >

Results are presented from tests of the third full-scale development dipole magnet for the Superconducting Super Collider (SSC) and from a retest of a 4.5-m model magnet of the same design mounted in an SSC cryostat. The 4.5-m magnet showed consistent quench performance between its original tests in boiling liquid helium in a vertical dewar and the current tests in forced-flow helium in a horizontal cryostat. Little or no retraining was observed over several thermal cycles. The full-length magnet required 12 quenches to train to its short-sample limit of 6800 A and displayed a reasonably stable quench plateau following training. Data are presented on quench behavior as a function of current and temperature, and on azimuthal and longitudinal loading of the coil by the support structure. >

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 authors measured the slow magnetization decay of short sample (2.3 cm) of Tevatron cable in fields up to 0.3 T. The special susceptometer in development for these measurements is based on a commercial SQUID (superconducting quantum interference device) and is described in detail. The observed decay is logarithmic in time as expected from flux creep in the NbTi filaments. A strong correlation was found between the decay and the magnetization status of the sample. It is too early yet to present a quantitative correlation between what the authors observed and the decay observed in the sextupole component of Tevatron dipoles. The detailed understanding of this phenomenon may be instrumental in guiding the search for efficient superconducting synchrotron operational procedures. >

The concept of a current meter for DC beams based on commercially available SQUIDs has been implemented and tested in a series of prototypes. One of them is expected to be used for monitoring the beam of our Antiproton Accumulator. After a brief explanation of the principles of operation, pick-up-loop design, magnetic and RF shielding considerations these prototypes and the experience acquired with them is described.

A special type of cryogenic current lead is described and its thermal evaluation is presented. This high voltage insulated lead was designed for heavy electrical conduction only during the quench of a superconducting magnet and for minimal heat leak.

We outline a new scheme for designing large planar gradiometers used in monopole searches by induction. With this scheme, the signal falls as 1 √L rather than as 1 L , where L is the inductance of the detector loop. The signal coupling in this scheme is better than is achievable in practice with conventional matching transformers. Also, segmentation facilitates the manufacture of bigger gradiometers. Results from prototype tests are reported and agree with calculation.

An experimental study of the normal zone propagation and total resistance as a function of time is described. The normal zone propagation velocity in a single strand was measured as a function of both current and magnetic field with particular interest in the neighborhood of the short sample limit. The study proceeded from measurements in single multifilamentary strands to measurements in 23 strand cables under different cooling environments to finally measurements in actual ramping dipole magnets made with this cable. Interpretation of the results led to the determination of safety limits for the Energy Doubler/Saver magnets and to safeguards implemented by an energy dumping circuit which effectively protects these magnets from self-destruction.

The lattice of the Fermi National Accelerator Laboratory's Energy Saver/Doubler contains a group of superconducting correction windings with each quadrupole which are housed in an element referred to as a "spool". There are 192 spools in the ring plus 12 special power spools which contain the main buss 5000 ampere power as well as correction elements. There will be constructed and tested 260 spools including spares of each of the eight different types. There have been 243 individual spools tested to date. During last fiscal year 188 spool tests were conducted at the test facility . The spools were tested for a) high voltage integrity, b) critical transport current, c) cryogenic heat load, d) cryogenic operating characteristics, e) thermometry calibration and at another facility, magnetic field quality. Data are summarized for 288 cryogenic tests of the 246 different spools, 488 coil sets, and 1464 correction magnets.

A superconducting magnet system testing area has been constructed above ground at the B12 location of the Fermilab main accelerator which facilitates the testing and development of superconducting magnet systems prior to committing their design to the full scale production Of the Doubler accelerator. The test results and operating experience of this system will be reported.

Two accelerator magnets have been designed and developed to a manufacturable prototype. Most of the dipole calculations presented will be based on a four shell, five kiloampere/turn, five centimeter aperature magnet, approximately six meters long. Two designs are considered: a dipole bending magnet and the quadrupole focusing magnet. The mechanical and electrical coil parameters are listed.

The current theoretical formulations of the three-phonon mechanism for the velocity dispersion and for the attenuation of sound in liquid He-4 are shown to be incompatible with new experimental data presented here.

Taking advantage of the recent advances in electronics we have developed a resistance thermometry system for the cryogenic environment of Fermilab’s Energy Saver Accelerator that fits in a natural way with its microcomputer based control logic. The system is based on measuring the voltage across a sensing resistor immersed in the cryogenic fluid while a current of 2.5 mA flows through it. High level signals (0.05 to 0.25 V) allows the use of integrated circuit multiplexers and reduces the relevance of thermal emf corrections. In order to prevent excessive self-heating of the sensor the current is kept on for a very short time (50 μs), just enough for it to stabilize. Near the end of the current pulse the voltage is sampled and held for an analog to digital conversion followed by storage in memory. The total operation is carried out in 100 μs. The repetition rate, 1 Hz, allows time for the sensing resistor to come again into thermal equilibrium with the surrounding fluid.

The first 16.5 m long SSC dipole magnet (D00001) had its field intensity measured as a function of position with a custom made NMR magnetometer. A short description of the probe is presented. The data obtained (most of it near 2 T spaced apart by one inch) shows an average transfer function of 1.02830 T/KA with position dependent values deviating from the average by up to .00130 T/KA revealing contruction inhomogeneities that were measured with a sensitivity of 25 ppM.