Henryk Piekarz

A Test of a 2 Tesla Superconducting Transmission Line Magnet System

A Superconducting transmission line magnet test system for the stage 1 accelerator of a staged VLHC proton-proton collider has been built and operated at Fermilab. The 1.5 m long, twin-aperture, combined function dipole magnet of 2 Tesla field is excited by a single turn 100 kA transmission line superconductor. The 100 kA dc current is generated using dc-dc switching converters powered by a bulk 240 kW supply. A pair of horizontally placed conventional leads facilitates transfer of this current to the magnet transmission line superconductor operating at liquid helium temperature. Fabrication of magnet components and magnet assembly work are described. The magnet test system and its operation are presented, and the performance is summarized

IOTA (Integrable Optics Test Accelerator): facility and experimental beam physics program

The Integrable Optics Test Accelerator (IOTA) is a storage ring for advanced beam physics research currently being built and commissioned at Fermilab. It will operate with protons and electrons using injectors with momenta of 70 and 150 MeV/c, respectively. The research program includes the study of nonlinear focusing integrable optical beam lattices based on special magnets and electron lenses, beam dynamics of space-charge effects and their compensation, optical stochastic cooling, and several other experiments. In this article, we present the design and main parameters of the facility, outline progress to date and provide the timeline of the construction, commissioning and research. The physical principles, design, and hardware implementation plans for the major IOTA experiments are also discussed.

Field Quality Measurements of a 2-Tesla Transmission Line Magnet

A prototype 2-Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. The 1.5 m long, combined-function gradient-dipole magnet has a vertical pole aperture of 20 mm. To measure the magnetic field quality in such a small magnet aperture, a specialized rotating coil of 15.2 mm diameter, 0.69 m long was fabricated. Using this probe, a program of magnetic field quality measurements was successfully performed. Results of the measurements are presented and discussed

The Development of 100 kA Current Leads for a Superconducting Transmission Line Magnet

A pair of current leads to power a transmission line magnet cooled at liquid helium temperature has been designed and developed at Fermilab. The leads were designed to carry 100 kA dc current. Each lead consists of a warm end, a heat exchanger section and a cold end. The warm end is a half moon shaped plate brazed to cylinder. The heat exchanger section is made of 202 copper rods arranged in a staggered pattern. Each rod is 6.35 mm in diameter and 1650 mm in length. The rods were soft-soldered into 12.7 mm deep holes at both warm and cold ends. The helium gas flow, guided by anodized aluminum baffles along the lead length, allows for a relatively high heat transfer coefficient between the current carrying rods and cooling helium gas. The current leads were successfully tested with a ramping current of up to 104 kA. The current lead design, assembly work and the test results are presented

Design Considerations for Fast-Cycling Superconducting Accelerator Magnets of 2 T B-Field Generated by a Transmission Line Conductor of up to 100 kA Current

Recently proposed synchrotrons, SF-SPS (Super- Ferric SPS) at CERN and DSF-MR (Dual Super-Ferric Main Ring) at Fermilab, would operate with a 0.5 Hz cycle (or 2 second time period) while accelerating protons to 480 GeV. We examine possibilities of superconducting magnet technology that would allow for an accelerator quality magnetic field sweep of 2 T/s. For superconducting magnets the AC losses in the coil compromise magnetic field quality and require high level of cryogenic cooling power. We outline a novel magnet technology based on HTS superconductors that may allow reduction of AC losses in the coil possibly up to an order of magnitude as compared to similar applications with LTS type conductors.

A Measurement of HTS Cable Power Loss in a Sweeping Magnetic Field

Short sample HTS power cable composed of multiple 344C-2G strands and designed to energize a fast-cycling dipole magnet was exposed to a sweeping magnetic field in the (2-20) T/s ramping rate. The B-field orientation toward the HTS strands wide surface was varied from to -4° to 8°, in steps of 10. The test arrangement allowed measurements of combined hysteresis and eddy current power losses of the cable assembly. For the validity of these measurements, the power losses of a short sample cable composed of multiple LTS wire strands were also performed and compared with the known data. The test arrangement of the power cable is described, and the test results are compared with the projections for the eddy and hysteresis power losses using fine details of the test cable structures.

Test Results of a 2 Tesla Superconducting Transmission Line Magnet Obtained With 102 Sensors Array of Hall Station

A prototype of a 2 Tesla superconducting transmission line magnet for future hadron colliders was designed, built and tested at Fermilab. This combined function magnet with a 4%/cm gradient and a 1.96 Tesla dipole field has a room temperature iron yoke with two horizontally separated air gaps for beam pipes. The magnetic field in both gaps is generated by a single-turn superconducting transmission line of 90 kA nominal current placed in the center of the iron yoke. The magnetic measurements were made simultaneously in both air gaps using a Hall Probe Station with 102 Hall sensors. The main parameters of Hall Station are briefly described. The magnetic design, pole tip and field quality optimization are presented. The iron saturation effects and their reduction with pole holes are also discussed. The results of magnetic measurements are compared with calculations, design parameters and the quality of magnetic field is discussed

Design, Construction, and Test Arrangement of a Fast-Cycling HTS Accelerator Magnet

Design, fabrication, and assembly of a novel fast-cycling accelerator magnet is presented. A short-sample magnet is powered with a single-turn HTS cable capable to carry 80-kA current up to a temperature of 20 K. This allows for a (13-15) K margin when using the operational temperature of (5-7) K. The availability of such a wide temperature margin for a fast cycling magnet constitutes the most necessary parameter for prevention and control of the fast-cycling magnet quench. Therefore, the HTS conductors have unsurpassed advantage over the LTS ones for which the maximum temperature margin is typically 2 K. The maximum possible generated field in the 40-mm test magnet gap is 1.75 T. The applied conventional leads and the power supply, however, allow only for the sin-wave 24-kA current of 20-Hz repetition rate, thus limiting magnet tests to the B-field of 0.5 T with a maximum cycling rate of 20 T/s. The critical aspects of cable construction and the splicing connection to the power leads are described. Tentative power losses of the proposed HTS-based accelerator magnet in possible applications for the proton and muon accelerators are presented.

USING TEVATRON MAGNETS FOR HE-LHC OR NEW RING IN LHC TUNNEL*

Two injector accelerator options for HE-LHC of p+ - p+ collisions at 33 TeV cms energy are briefly outlined. One option is based on the Super-SPS (S-SPS) [1] accelerator in the SPS tunnel, and the other one is based on the LER (Low-Energy-Ring) [2] accelerator in the LHC tunnel. Expectations of performance of the main arc accelerator magnets considered for the construction of the S-SPS and of the LER accelerators are used to tentatively devise some selected properties of these accelerators as potential injectors to HE-LHC.

Design Study and Test Arrangement of HTS Transmission Line Power Cable for Fast Cycling Accelerator Magnets

Designs of the HTS transmission line power cable and the matching magnetic core for a fast-cycling accelerator dipole magnet are presented. The hysteretic and eddy currents induced power losses of the proposed HTS cable operating under various sweeping magnetic fields are projected and compared to those of the LTS cable in similar applications. The engineering design of the HTS power cable for the fast cycling dipole magnet is presented, and the test arrangement of a short-sample cable operating under the sweeping magnetic field is described.