55170241
Superconducting solenoids for an international muon cooling experiment
ASC-2002, Paper 4LL02 Superconducting Solenoids for an International Muon Cooling Experiment* M. A. Green, and J. M. Rey Abstract— The international muon ionization cooling experiment MICE will consist of two focusing cooling cells and a pair of uniform field solenoids used for particle identification and emittance measurements. The 2.75-meter long cooling cells have a pair of field flip coils and a coupling coil. The 0.52-meter diameter field flip coils surround an absorber that removes transverse and longitudinal momentum from the muons to be cooled. The beam in the absorber is at a minimum beta point so that scattering of the muons is minimized. The 1.7-meter diameter coupling coils are outside of conventional 201.25 MHz RF cavities that accelerate the muons putting longitudinal momentum into the muons without putting back the transverse momentum into the beam. A third set of flip coils helps the muon beam transition from and to the experimental solenoids. The 0.6-meter diameter experimental solenoids have a uniform field region (good to about 1 part in 1000) that is 1.3-meters long. The MICE experiment magnets must operate as a single unit so that the field profile will produce the maximum muon cooling. Index Terms—Superconducting Solenoids, and Muon Cooling II. T HE P ROPOSED MICE E XPERIMENT The proposed MICE experiment will test cooling on a low intensity muon beam from an existing accelerator. It is probable that the MICE will be done at the Rutherford Appleton Laboratory in the United Kingdom. The pions that decay to muons are produced by dipping a target into the ISIS proton beam. The Pions will decay into a well-defined beam of muons. The muon beam will be carried to an experimental hall containing the MICE. The beam enters the experiment by passing through a foil that will scatter the muon to produce a beam of desired emittance. The muon emittance will be measured by either a time projection chamber (TPC) or four planes of scintillating fibers that are in a uniform solenoidal magnetic field of about 4 T. The required magnetic field uniformity depends on the type of detector selected. Fig. 1 shows a view of MICE. Once the emittance of the muon beam entering the cooling section has been measured, the beam passes through an absorber that cools the muon beam by ionization cooling. The absorber is in a field flip region (where the direction of the field reverses) so that the beam beta can be minimized. The absorber may be liquid hydrogen, liquid helium, lithium hydride, lithium, or plastic. The preferred absorber material is liquid hydrogen, because it has the lowest multiple scattering of any of the absorber materials for a given energy absorption and beam beta. Comparable performance from lithium or lithium hydride requires a cooling lattice that produces the lowest possible beam beta. The use of liquid hydrogen absorbers presents the design team with safety issues, with which many sites do not want to deal. The muon beam momentum is recovered by accelerating the beam with a four cell 201.25 MHz RF cavity that is in a 2.5 to 3 T magnetic field. After the muon beam has been re- accelerated, it passes through a second absorber in a second field flip region. The process of re-acceleration is repeated then the beam passes through the final absorber and field flip solenoid. At this point, the muon beam should be cooled so that the cooling can be clearly measured. The MICE cooling cells are almost identical to the 2.75-m long muon cooling cells in the level 2 study of the neutrino factory [3] [4]. Once the beam has passed through the ionization cooling section, it enters a second detector section. The second detector section is identical to the first detector, except for the time of flight detectors at the end of the experiment. A critical problem for the MICE experiment is matching between the detectors and the muon cooling section. . I NTRODUCTION he development of a muon collider or a neutrino factory requires that beams of low emittance muons be produced. A key to the production of low emittance muons is muon cooling. A demonstration of muon cooling is essential to the development of muon accelerators and storage rings. The international Muon Ionization Cooling Experiment (MICE) will be a demonstration of muon cooling in a configuration that may be useful for either a neutrino factory [1] or a muon collider [2]. Ionization cooling of muons means that muons have their momentum reduced in both the longitudinal direction and the transverse direction by passing them through a low Z absorber. RF cavities are used to re-accelerate the muons to their original momentum. If the scattering in the absorbing medium is not too large, the reaccelerated muon beam will have a lower emittance than the muon beam that entered the absorbers. In order to reduce the multiple scattering of the muon beam in the absorber, the muon beam beta in the absorber must be low and the absorber must have a low Z. The possible absorbers include liquid hydrogen, liquid helium, lithium hydride lithium metal or polyethylene. T Manuscript received 6 August 2002. The M. A. Green is from the Lawrence Berkeley National Laboratory, Berkeley CA 94720 USA. J. M. Rey is from CEN Saclay, 91191 Gif-sur-Yvette, France. *This work was performed at the Lawrence Berkeley Laboratory with the support of the Office of Science at the Department of Energy under DOE contract number DE-AC03-76SF00098 .
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.
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. >
122003703
Quench back in thin superconducting solenoid magnets
Abstract Superconducting magnets with well coupled, low resistance, secondary circuits have been observed to become fully normal faster than quench propagation in the coil would permit. This process is referred to as ‘quench back’. Quench back observed at the Lawrence Berkeley Laboratory (LBL) was caused by heating the secondary circuit from the current induced from the primary circuit as normal region in the superconducting coil propagated. This paper develops the theory for thermal quench back in thin solenoid magnets and compares this theory with measurements made in two one-meter diameter superconducting solenoid magnets.
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
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ACTIVE CENTER TAP QUENCH PROTECTION
92416193
Observation of phi°phi° production in 400-GeV/c proton-proton interactions
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.