55055434
A heat exchanger between forced flow helium gas at 14 to 18 K and liquid hydrogen at 20 K circulated by natural convection
LBNL-53719 A HEAT EXCHANGER BETWEEN FORCED FLOW HELIUM GAS AT 14 TO 18 K AND LIQUID HYDROGEN AT 20 K CIRCULATED BY NATURAL CONVECTION M. A. Green 1 , S. Ishimoto 2 , W. Lau 3 , and S. Yang 3 Lawrence Berkeley National Laboratory, Berkeley CA 94720, USA KEK, 1-1 Oho, Tsukuba, 305-0801, Japan, Oxford University, OX1, 2JD, Oxford UK ABSTRACT The Muon Ionization Cooling Experiment (MICE) has three 350-mm long liquid hydrogen absorbers to reduce the momentum of 200 MeV muons in all directions. The muons are then re-accelerated in the longitudinal direction by 200 MHz RF cavities. The result is cooled muons with a reduced emittance. The energy from the muons is taken up by the liquid hydrogen in the absorber. The hydrogen in the MICE absorbers is cooled by natural convection to the walls of the absorber that are in turn cooled by helium gas that enters at 14 K. This report describes the MICE liquid hydrogen absorber and the heat exchanger between the liquid hydrogen and the helium gas that flows through passages in the absorber wall. INTRODUCTION The muon ionization cooling experiment (MICE) uses liquid hydrogen absorbers to absorb energy from a beam of 200 MeV/c muons. This energy absorbed is in both the longitudinal and the transverse directions. Energy is put back into the muons in the longitudinal direction. If the heating due to scattering is less than the cooling through absorption, there is net cooling of the muon beam. In order to minimize scattering, liquid hydrogen or liquid helium is used as an absorber. In addition, the absorber is put into a two- coil solenoid that generates a cusp shaped magnetic field. The magnet that generates this magnetic field is described in references [1] and [2]. The MICE absorber is buried in the bore of a superconducting gradient solenoid magnet. Heat from the beam and heat leaks into the absorber is removed by a stream of helium gas that enters the absorber shell at 14 K. The exit temperature for the gas depends on the total amount of heat that is to be put into the absorber and the mass flow of the helium gas that passes through the heat exchanger in the absorber shell. The sub-cooled hydrogen that is in the absorber body is cooled by natural convection heat transfer to the absorber wall. The heat exchange surface on both sides of the hydrogen vessel wall is extended in order to improve the heat transfer between the sub-cooled liquid in the absorber and the helium flowing in the heat exchanger on the outside of the absorber. The absorber system is also designed so that the absorber can contain sub-cooled liquid helium in place of the hydrogen. FIGURE 1 shows an end view of the hydrogen absorber inside of the superconducting solenoid warm bore.
24392991
The Engineering Design of the 1.5 m Diameter Solenoid for the MICE RFCC Modules
The RF coupling coil (RFCC) module of MICE is where muons that have been cooled within the MICE absorber focus (AFC) modules are re-accelerated to their original longitudinal momentum. The RFCC module consists of four 201.25 MHz RF cavities in a 1.4 meter diameter vacuum vessel. The muons are kept within the RF cavities by the magnetic field generated by a superconducting coupling solenoid that goes around the RF cavities. The coupling solenoid will be cooled using a pair of 4 K pulse tube cooler that will generate 1.5 W of cooling at 4.2 K. The magnet will be powered using a 300 A two-quadrant power supply. This report describes the ICST engineering design of the coupling solenoid for MICE.
118834673
A Design for a Combined Function Superconducting Dipole for a Muon Collider FFAG Accelerator
The acceleration stages for a muon collider require that the muons be accelerated within a given ring in fewer than twenty turns. One type of accelerator that appears to be attractive for a synchrotron that accelerates the muon a factor of four in energy in a few turns is the Fixed Field Alternating Gradient (FFAG) type of accelerator. As the energy of the muon beam increases, the muons move toward a higher field region of a DC combined function dipole. The following dipole and quadrupole magnet characteristics are required for a muon FFAG machine to be successful: (1) The dipole will be a fixed field dipole with an impressed quadrupole and sextupole field. There may or may not be separate quadrupoles that mayor may not have added sextupole windings. (2) The horizontal aperture of the required good field region is wider than the vertical aperture of the required good field region. (3) The magnet is relatively short, so that the conventional SSC type of superconducting dipole or quadrupole ends can not be used. The field at the end of the magnet must fall off abruptly within the distance of less than one vertical aperture. For a magnet that is 400more » mm long, the end region can be no more than 80 mm long. (4) The structure of the integrated field within the end region must be the same as the structure of the two-dimensional filed at the center of the magnet. A very preliminary design concept for a FFAG combined function dipole is presented in this paper.« less
122748175
Calculation of the pressure rise in the cooling tube of a two-phase cooling system during a quench of an indirectly cooled superconducting magnet
Large superconducting detector magnets are indirectly cooled with two-phase helium flowing in cooling tubes attached to the coil or its support structure. Large detector magnets often quench such that most of the magnet stored energy ends up as heat stored in the coil package. The time constant for energy deposition in the coil and support structure is often quite short. This paper presents a method for calculating the peak pressure rise in the magnet two-phase cooling tube during a magnet quench. A comparison of calculated peak pressure rise and measured pressure rise for the PEP-4 solenoid is presented in this report. >
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
123081787
PROGRESS ON THE SUPERCONDUCTING MAGNET FOR THE TIME PROJECTION CHAMBER EXPERIMENT (TPC) AT PEP
The TPC (Time Projection Chamber) experiment at PEP will have a two meter inside diameter superconducting magnet which creatests a 1.5 T uniform solenoidal field for the TPC. The superconducting magnet coil, cryostat, cooling system, and the TPC gas pressure vessel (which operatests at 11 atm) were designed to be about two thirds of a radiation length thick. As a result, a high current density coil design was chosen. The magnet is cooled by forced flow two phase helium. The TPC magnet is the largest adiabatically stable superconducting magnet built to date. The paper presents the parameters of the TPC thin solenoid and its subsystems. Tests results from the Spring 1980 cryogenic tes are presented. The topics to be dealt with in the paper are cryogenic services and the tests of magnet subsystems such as the folded current leads. Large thin superconducting magnet technology will be important to large detectors to be used on LEP.
32857257
Conditions for successful extended inflation.
We investigate, in a model-independent way, the conditions required to obtain a satisfactory model of extended inflation in which inflation is brought to an end by a first-order phase transition. The constraints are that the correct present strength of the gravitational coupling is obtained, that the present theory of gravity is satisfactorily close to general relativity, that the perturbation spectra from inflation are compatible with large scale structure observations, and that the bubble spectrum produced at the phase transition does not conflict with the observed level of microwave background anisotropies. We demonstrate that these constraints can be summarized in terms of the behavior in the conformally related Einstein frame, and can be compactly illustrated graphically. We confirm the failure of existing models including the original extended inflation model, and construct models, albeit rather contrived ones, which satisfy all existing constraints.
45476268
Observation of double phi-meson production in 400-GeV/c proton-nucleon interactions.
The production of phi-meson pairs has been observed in 400-GeV/c proton-nucleon interactions at the Fermilab multiparticle spectrometer in the inclusive reaction pN..-->..phiphi+X, where each phi decays to a K/sup +/K/sup -/ pair. A fast (200 nsec)= high-level processor was used to selectively trigger on events containing two pairs of oppositely charged kaons having low invariant masses. The experimental apparatus and trigger processor are described. The cross section for phiphi production and an upper limit for eta/sub c/ production are presented.
92416193
Observation of phi°phi° production in 400-GeV/c proton-proton interactions