Yuenian Huang

Design and commissioning of Fermilab's vertical test stand for ILC SRF cavities

As part of its ILC program, Fermilab is developing a facility for vertical testing of SRF cavities. It operates at a nominal temperature of 2 K, using a cryoplant that can supply LHe in excess of 20 g/sec and provide bath pumping capacity of 125 W at 2 K. The below-grade cryostat consists of a vacuum vessel and LHe vessel, equipped with magnetic shielding to reduce the ambient magnetic field to ≪10mG. Internal fixed and external movable radiation shielding ensures that exposure to personnel is minimzed. The facility features an integrated personnel safety system consisting of RF switches, interlocks, and area radiation monitors.

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

HINS Linac Front End Focusing System R&D

This report summarizes current status of an R&D program to develop a focusing system for the front end of a superconducting RF linac. Superconducting solenoids will be used as focusing lenses in the low energy accelerating sections of the front end. The development of focusing lenses for the first accelerating section is in the production stage, and lens certification activities are in preparation at FNAL. The report contains information about the focusing lens design and performance, including solenoid, dipole corrector, and power leads, and about cryogenic system design and performance. It also describes the lens magnetic axis position measurement technique and discusses scope of an acceptance/certification process.

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.

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.

Design Considerations of a Pair of Power Leads for Fast-Cycling Superconducting Accelerator Magnets Operating at 2 Tesla and 100 kA

Recently proposed injector accelerator, Low Energy Ring (LER) for the LHC and fast cycling accelerators for the proton drivers, SF-SPS at CERN and Dual Super-Ferric-Main Ring (DSF-MR) at Fermilab of neutrino sources require that a new magnet technology be developed. In support of this accelerator program, a pair of power leads needs to be developed to close the loop between the power supply and accelerator system. The magnet proposed to be used will be a modified transmission line magnet technology that would allow for accelerator quality magnetic field sweep of 2 T/s. The transmission line conductor will be using HTS technology and cooled with supercritical helium at 5 K. The power leads consist of two sections; upper one is a copper and lower section will be using HTS tapes. The accelerator magnet will be ramped to 100 kA in a second and almost immediately ramped down to zero in one second. This paper outlines the design considerations for the power leads to meet the operational requirements for the accelerator system. The power leads thermal analysis during the magnet powering cycle will be included.

A Cryogenic test stand for LHC quadrupole magnets

A new test stand for testing LHC interaction region (IR) quadrupole magnets at the Fermilab Magnet Test Facility has been designed and operated. The test stand uses a double bath system with a lambda plate to provide the magnet with a stagnant bath of pressurized He II at 1.9 K and 0.13 MPa. A cryostated magnet 0.91 m in diameter and up to 13 m in length can be accommodated. This paper describes the system design and operation. Issues related to both 4.5 K and 1.9 K operations and magnet quenching are highlighted. An overview of the data acquisition and cryogenics controls systems is also included.

CRYOGENIC INFRASTRUCTURE UPGRADE OF THE FERMILAB MAGNET AND VERTICAL CAVITY TEST FACILITIES

The Fermilab Magnet Test Facility (MTF) and the Vertical Cavity Test Facility (VCTF), both located in Industrial Building 1 and serviced by a shared cryogenic infrastructure, provide cryogenic testing of superconducting magnets and superconducting radio‐frequency cavities in support of programs such as the Tevatron, US‐LHC, LARP, HINS, Project X, and the ILC. While MTF must continue to support a robust magnet test program, VCTF is expected to increase its cavity test throughput by a factor of five, reaching 250 cavity test cycles per year as cavity production ramps up. A cryogenic infrastructure upgrade program has been undertaken in preparation for meeting the challenge of this additional cavity test throughput. The cryogenic infrastructure improvements include dedicated ambient temperature vacuum pumps, a helium compressor, purification skids, and additional helium gas storage. This paper will elaborate on the goals of the upgrade program, the selected equipment, and foreseen integration and operations ...

HTS Power Lead Testing at the Fermilab Magnet Test Facility

The Fermilab Magnet Test Facility has tested high-temperature superconductor (HTS) power leads for cryogenic feed boxes to be placed at the Large Hadron Collider (LHC) interaction regions and at the new BTeV C0 interaction region of the Fermilab Tevatron. A new test facility was designed and operated, successfully testing 20 pairs of HTS power leads for the LHC and 2 pairs of HTS power leads for the BTeV experiment. This paper describes the design and operation of the cryogenics, process controls, data acquisition, and quench management systems. Results from the facility commissioning are included, as is the performance of a new insulation method to prevent frost accumulation on the warm ends of the power leads.