108163413
Progress on the MICE RFCC Module for the MICE Experiment
PROGRESS ON MICE RFCC MODULE FOR THE MICE EXPERIMENT* Allan DeMello, Nord Andresen, Michael Green, Derun L i , Heng Pan, Steve Virostek, Michael Zisman ( L B N L , Berkeley C A 94720, USA), Don Summers, Mike Reep (University of Mississippi, Oxford M S 38677, USA) An Bin Chen, Xiao-Kun Liu, Feng-Yu X u , Shi-Xian Zheng (HIT, Harbin, China), Yun Cao, Sen Sun, L i Wang, Lixin Y i n (SINAP, Shanghai, China) Abstract We describe the recent progress on the design and fabrication of the R F C C (RF and Coupling Coil) module for the international Muon Ionization Cooling Experiment (MICE). The M I C E cooling channel has two R F C C modules; each has four 201-MHz normal conducting R F cavities and one superconducting solenoid magnet. The magnet is designed to be cooled by three cryocoolers. Fabrication of the R F cavities is complete; design and fabrication of the magnets are in progress. The first magnet is expected to be finished by the end of 2011. pneumatic actuator (Fig. 3). Six flexure tuners are currently being fabricated (University of Mississippi) for a full cavity test of the R F tuner system. This test will include the electronic pressure control, EPICS software interface and the R F feedback system. This system will be assembled into a single cavity vacuum vessel (see below) for testing. INTRODUCTION M I C E is an international experiment designed to demonstrate muon beam cooling using ionization cooling (Fig. 1). Muons are captured in a strong magnetic field, cooled in 4D phase space and re-accelerated in the beamline direction by the normal conducting R F cavities in the R F C C . This demonstration is key to the success of a future Neutrino Factory or Muon Collider. The experiment is being hosted at Rutherford Appleton Laboratory ( R A L ) in the U K , where beamline commissioning is underway. Institutions participating in the collaboration include national laboratories and universities in Europe, the U.S., China, and Japan. Figure 2: 90° sectioned view of the M I C E cooling channel R F C C module. Figure 1 : The M I C E cooling channel. RFCC M O D U L E CAVITIES Lawrence Berkeley National Laboratory is responsible for the design of the R F Cavity and Coupling Coil (RFCC) module for M I C E (Fig. 2). Each R F C C module will contain four 201 M H z normal conducting R F cavities and one superconducting coupling coil magnet [4]. Each cavity will have its frequency actively tuned using six stainless steel flexure tuners moved with a dual action * This work was supported by the Office of Science, U.S. Department of Energy under D O E contract number DE-AC02-05CH11231. Figure 3: The prototype RF tuner flexure and actuator mounted on a 201-MHz cavity.
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
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. >
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.
16611628
D-instanton induced interactions on a D3-brane
Non-perturbative features of the derivative expansion of the effective action of a single D3-brane are obtained by considering scattering amplitudes of open and closed strings. This motivates expressions for the coupling constant dependence of world-volume interactions of the form (∂F)4 (where F is the Born-Infeld field strength), (∂2)4 (where are the normal coordinates of the D3-brane) and other interactions related by = 4 supersymmetry. These include terms that transform with non-trivial modular weight under Montonen-Olive duality. The leading D-instanton contributions that enter into these effective interactions are also shown to follow from an explicit stringy construction of the moduli space action for the D-instanton/D3-brane system in the presence of D3-brane open-string sources (but in the absence of a background antisymmetric tensor potential). Extending this action to include closed-string sources leads to a unified description of non-perturbative terms in the effective action of the form (embedding curvature)2 together with open-string interactions that describe contributions of the second fundamental form.
2191534
Symmetry breaking at enhanced symmetry points
The influence of world-sheet boundary condensates on the toroidal compactification of bosonic string theories is considered. At the special points in the moduli space at which the closed-string theory possesses an enhanced unbroken G × G symmetry (where G is a semi-simple product of simply laced groups) a scalar boundary condensate parameterizes the coset G × G/G. Fluctuations around this background define an open-string generalization of the corresponding chiral nonlinear sigma model. Tree-level scattering amplitudes of on-shell massless states (‘pions’) reduce to the amplitudes of the principal chiral model for the group G in the low energy limit. Furthermore, the condition for the vanishing of the renormalization group beta function at one loop results in the familiar equation of motion for that model. The quantum corrections to the open-string theory generate a mixing of open and closed strings so that the coset-space pions mix with the closed-string G × G gauge fields, resulting in a Higgs-like breakdown of the symmetry to the diagonal G group. The case of non-oriented strings is also discussed.
108681531
A 2-MeV microwave thermionic gun
A high-gradient, S-band microwave gun with a thermionic cathode is being developed in a collaborative effort by AET, Varian, and SSRL. A prototype design using an upgraded Varian dispenser cathode mounted with thermal isolation directly in the first half-cell of a 1-1/2 cell, side-coupled, standing-wave cavity has been fabricated and is being tested. Optimization of the cavity shape and beam formation was done using SUPERFISH, MASK, and PARMELA. An overview of design details, as well as the status of in-progress beam tests, will be presented. 9 refs., 6 figs.
122961674
Infinity Cancellations in SO(32) Superstring Theory
Abstract Type I superstring theory was previously shown to be anomaly-free if the gauge group is SO(32). Here it is demonstrated that the same group is also singled out by the requirement that infinities can be canceled by combining diagrams.
122955461
The structure of superstring field theories
Abstract Superstring field theories involve two basic types of local interactions, which may be regarded as string generalizations of a cubic Yang-Mills coupling and a cubic gravity coupling. The higher-order contact terms of the low-energy effective supergravity field theories arise from the exchange of massive superstring states.