Clyde Taylor

The use of pressurized bladders for stress control of superconducting magnets

LBNL is using pressurized bladders in its high field superconducting magnet program Magnet RD3; a 14 T race track dipole, has been assembled and pre-stressed using such a system. The bladder, placed between the coil pack and the iron yoke, can provide 70 MPa of pressure while compressing the coil pack and tensioning a 40 mm thick structural aluminum shell. Interference keys replace the bladders functionality as they are deflated and removed leaving the shell in 140 MPa of tension. During cool down, stress in the shell increases to 250 MPa as a result of the difference in thermal expansion between the aluminum shell and the inner iron yoke. A number of strain gauges mounted onto the shell were used to monitor its strain during assembly, cool-down and testing. This technique ensures that the final and maximum stress in the shell is reached before the magnet is ever energized. The use of a structural shell and pressurized bladders has simplified magnet assembly considerably. In this paper we describe the bladder system and its use in the assembly of a 14 T Nb/sub 3/Sn magnet.

The Design Parameters for the MICE Tracker Solenoid

The first superconducting magnets to be installed in the union ionization cooling experiment (MICE) will be the tracker solenoids. The tracker solenoid module is a five coil superconducting solenoid with a 400 mm diameter warm bore that is used to provide a 4 T magnetic field for the experiment tracker module. Three of the coils are used to produce a uniform field (up to 4 T with better than 1 percent uniformity) in a region that is 300 mm in diameter and 1000 mm long. The other two coils are used to match the muon beam into the MICE cooling channel. Two 2.94-meter long superconducting tracker solenoid modules have been ordered for MICE. The tracker solenoid will be cooled using two-coolers that produce 1.5 W each at 4.2 K. The magnet system is described. The decisions that drive the magnet design will be discussed in this report.

The Design and Construction of the MICE Spectrometer Solenoids

The purpose of the MICE spectrometer solenoid is to provide a uniform field for a scintillating fiber tracker. The uniform field is produced by a long center coil and two short end coils. Together, they produce 4T field with a uniformity of better than 1% over a detector region of 1000 mm long and 300 mm in diameter. Throughout most of the detector region, the field uniformity is better than 0.3%. In addition to the uniform field coils, we have two match coils. These two coils can be independently adjusted to match uniform field region to the focusing coil field. The coil package length is 2544 mm. We present the spectrometer solenoid cold mass design, the powering and quench protection circuits, and the cryogenic cooling system based on using three cryocoolers with re-condensers.

Preliminary Test Results for the MICE Spectrometer Superconducting Solenoids

This report describes the MICE spectrometer solenoids as built. Each magnet consists of five superconducting coils. Two coils are used to tune the beam going from or to the MICE spectrometer from the rest of the MICE cooling channel. Three spectrometer coils (two end coils and a long center coil) are used to create a uniform 4 T field (to plusmn0.3 percent) over a length of 1.0 m within a diameter of 0.3 m. The three-coil spectrometer set is connected in series. The two end coils use small power supplies to tune the uniform field region where the scintillating fiber tracker is located. This paper will present the results of the preliminary testing of the first spectrometer solenoid.

VENUS: The next generation ECR ion source

The construction of VENUS, an Electron Cyclotron Resonance ion source designed to operate at 28 GHz, is nearing completion. Tests with the superconducting magnet assembly produced axial magnetic field strengths of 4 T at injection and 3 T at extraction and a sextupole field of 2 T at the plasma wall. These fields are sufficient for optimum operation at 28 GHz. We expect a shift to higher charge states and an increase in the beam intensities (about 4 times) compared to those obtained with the AECR-U, which operates at 14 GHz. Initial operation will be at 18 GHz, but best performance is expected when operation with a 10 kW, 28 GHz gyrotron becomes possible. The high beam intensities and the large axial magnetic field at extraction make it challenging to extract, analyze and transport the beam into the 88-Inch Cyclotron. The analyzing system which consists of a solenoid lens and a large gap 18 cm spectrometer-magnet with higher order field corrections has been optimized utilizing 3D magnet and ray-tracing codes including space charge effects. The status of the construction and design aspects of the source and beam transport system are described below.

A Proposed IR Quad for the SSC

This note outlines a detailed magnetic design of a high-gradient quadrupole for the beam interaction region of the SSC. The 58 mm bore, 2 layer magnet uses 36 strand cable identical to the collider dipole magnet outer cable, thin collars, a close-fitting iron yoke, and a shell for structural support. With a 1.3:1 Cu/Sc ratio the quadrupole short sample gradient is 274 T/m at 1.9 K and 209.7 T/m at 4.35 K with good field quality. Assembled with 7 mm collars, the magnet is placed inside a four-segment iron yoke and prestressed with welded outer shell. Prestress is maintained during cooldown by aluminum spacers placed between the segmented iron yoke blocks. This paper describes various conceptual design details including coil geometry, load line and margin, field uniformity and saturation effects.

New concept for a high-power beam dump☆

Abstract A new concept for a dump for the ion and neutral beams used in the controlled nuclear fusion program uses thin sheets of a refractory metal such as tungsten formed into troughs having semi-circular cross sections. High-velocity water flowing circumferentially removes heat by subcooled nucleate boiling. Possible advantages are modular construction, relatively long sputtering lifetime, and a lower pressure drop than in tubular beam dumps. An example design calculation is shown for a dump estimated to be capable of absorbing an incident flux of 10 kW/cm 2 with reasonable safety factors.