120458015
LARGE SUPERCONDUCTING DETECTOR MAGNETS WITH ULTRA THIN COILS FOR USE IN HIGH ENERGY ACCELERATORS AND STORAGE RINGS
LARGE SUPERCONDUCTING DETECTOR MAGNETS WITH ULTRA THIN COILS FOR USE IN HIGH ENERGY ACCELERATORS MiD STORAGE RINGS. H. A, Green Lawrence Bemeley Laboratory llo1.versity of California Beme1ey, california MASlIR This paper describes the development of a ni!W class of large superconducting soleiwid magJ!l!ts. High energy physics on colJ,iding beam machines sometimes require the use of thin coH' solenoid magnets. ,The development of these ,magnets bas proceeded with the substitution of li'ght materials for heavy materials and by ,inCrea9ing the current density in the coils. The Lawrence Beme1ey Laboratory bas developed a 1:adtca1 approach to the pEOblem by ba'ldng the co11 operate at very high cur1:ent, densities. This approach and its implications are described in detail. Introduction Recent'developments in colliding beam physics have prompted the development of thin superconductiog solenoid magnets for use ia these experiments. The development of thin m3g0ets can be traced starting with PLUTO, the fi1:st superconducting magnet which was used to do colliding beam physics. The evolution of thin coil technology can be trsced by comparing PLUTO (which is not a thin superconducting magnet) with three other superconductiog magnets which have been built OT are being built for colliding beam experiments. All tbree of these magnets are 'designed to be thin to some degtee. A comparative' study of the four magnets illustrstes the trend of thin supercooducting co11 development over tbe last two D1: three years. first, Doe sees tbe substitution of lighter materials for heavier msterials in the CERN magnet. Then ooe sees the abandoDlll!nt of cryogeoic stsbility wben the batb cryostat is replaced witb tbe tubular cooling system in the CELLO magnet. F1oslly, tbe conductive bore tube concept is introduced in order to make a radical improvement in the ,protection' of thin solenoid magnets against burnout. This is the basis of the TPC magnet design proposed by the Lawrence Berkeley Laboratory (LBL). Over half of this pap'er will be devoted to the LBL magnet 'technique. Since the LBL tecb- nique is a radical departure from conventioosl technique, this paper will present tbe theory of the conductive bore tube and discuss the resulta of experiments on LBL test coils. Three test c.oils· have been c.onstruc.ted at LBL. Two of these coUs, each with a diameter of one meter. have been fully tested and the results are presented herein. Preliminsry tests on the third test 'magnet, which bas a diameter of two meters, are described. The results' of these tests show the viability of the LBL two-phase tubular cooling system and the conductive bore tube for diverting the magnetic current from the superconducting coil. The LBL technique ia applicable to magnets in a variety of sizes. The radiation thickness attainable is a function of diameter and central induction. Thia relaticoship is sbown in this pape::. In addition, one can apply light sUperconductors and conductive bore tubes. This can, in principle, result in reduction of the radiation thickness of solenoids whicb bave a diam- eter below a certain value. t a The development of thin solenoid technology The 'development of thin nagnet technology can be traced by comparing four colliding beam detector solenoids which have been built or are about to te built. The first of these magnets is PLUTO. This magnet, which makes no effort to bj! thin, was built in 1971 using tbe conductor and stabilization technology used in the large bubble cbsmber(l). The second magnet, ISR, built by Horpurgoat' CERN' in 1976, Bub Q !ltuted a cryt;>genica11y stabilized allllll1J1um conductor for th~ ciJpperc< iductor normally used l ). The vacuum ve,.sela and cryostat vessels are also msde of aluminum; The third step iil this progression is the msgnet, proposed for the CELLO elCPertment by !;aclsy and',Karlsrube using ilitrinaically stable aluminum conductor which operates 'at current densitieS' of 1.4 x 108 &-2(3). The fourth step 1n the progress10n is represented by the magni!t proposed for the time projectiOn cblllltJer (TPC) experiment by the Lawrence Beme1ey Laboratol.y(4). This magDet, uses superconductor at very high matrix current densities (about 109 Am- 2 h' - The msgriet uses a tVo-pbase tubular COOling system. The ,four magnets ':e clllllpsred in Table 1. The PLUTO magnet bas the largest central inductiOn 'and ~est free wI ,. ,The TPC magnet has both the,largest free volume and stored eaergy. The ISR '!liagnet bas the alliallest stored energy end i t has a central induction of 1.S T lik'l the CELLO ana' TPC magnets. The thiekeBt magnet from a radiation standpOint is' the PLUTO magnet. The,' thinnest magnet ia the TPC magnet. * Work performed urier tbe auspices of U.S. Energy Research and Develo~,,\,!l'S ~~ois~st1oi? .. ' UI.:j ~ ,(Ial l 110. 1 ,ur ,U'.I~' t..U
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. >
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.
94844521
ACTIVE CENTER TAP QUENCH PROTECTION
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
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.
119025667
Quantum Corrections to Eleven-Dimensional Supergravity
122187455
Superfield theory of type (II) superstrings
Abstract Type (II) superstrings are described by light-cone superfields that are functionals of string superspace coordinates x i ( σ ) and ϑ a ( σ ) or the conjugate momenta p i ( σ ) and λ a ( σ ). The interaction hamiltonian and supersymmetry charges are determined to first order in the coupling constant by requiring invariance under the super-Poincare algebra, some of whose generators are implemented locally in σ. In a suitable low-energy limit the formalism goes smoothly into that of extended supergravity in ten dimensions.
119955549
Point-like structure and off-shell dual strings
Abstract We argue that in a consistent off-shell dual formalism the amplitude for the emission of a scalar off-shell state by a string consists of two components. One of these contains the particle poles in the off-shell leg and the other is intimately related to the insertion of a point-like energy density on the string. As a result, the amplitude for a string to emit a zero momentum scalar state into the vacuum (which may be relevant for spontaneous symmetry breaking) is described by the amplitude for a finite fraction of the energy in the string to collapse to a spatial point at some time (this fraction and its space-time position being integrated over). The off-shell amplitudes have an elegant formulation in terms of a set of “confined modes” which can be assigned quark flavour quantum numbers to reproduce the Chan-Paton scheme. We suggest the dual model be modified by allowing for the coupling of scalar closed strings to the vacuum and the resulting effect on the space-time structure of dual Green functions is described. We find that even the emission of a single zero-momentum closed string modifies the elastic amplitude in a significant manner, leading to a power-behaved fixed-angle cross section in contrast to the usual exponential decrease of the dual model. This arises from point-like scattering between energy densities accumulating in the colliding strings. The relationship between the fixed angle and Regge limits is discussed. The fixed angle behaviour is found to be the asymptotic limit in momentum transfer of a fixed pole that arises in the Regge limit.
120913474
Quantum mechanics of a twisted superparticle
Abstract This paper is devoted to the quantization of the ten-dimensional superparticle in the formulation, due to Siegel, in which the local fermionic symmetry is implemented using explicit gauge fields and in which momentum coordinates conjugate to the fermionic superspace coordinates are introduced. Here, a truncation of the complete N = 1 superparticle is considered (the complete superparticle is analysed in a separate paper). This “truncated model” (which was the first modified superparticle considered by Siegel) is shown to be invariant under a “twisted” N = 2 space-time supersymmetry, and a light-cone gauge analysis shows that the physical spectrum is a representation of this algebra which includes negative norm states. The Batalin-Vilkovisky method is used to covariantly quantize the system in two ways, one with an infinite number of ghost fields and one with only a finite number. In both cases, the BRST cohomology is analysed in detail. Our results illustrate certain general features: (i) In a formulation with gauge fields for the fermionic symmetries the invariance can be fixed by imposing gauge conditions on the gauge fields. This results in a free quantum action, without the need for the problematic field redefinitions that arise in earlier formulations in which gauge conditions are imposed on the spinorial coordinates. (ii) There is an interesting pattern for the infinite number of ghost-for-ghosts, which naturally divide into two sets. The first is an infinite sequence of gauge fields while the second is a set of ghosts for the corresponding sequence of gauge invariances. (iii) The infinite set of quantum fields packages into simple infinite-dimensional spinor representations of the supergroup OSp(9, 1 | 2). The cohomology classes are particularly easy to describe in terms of OSp(9, 1 | 2) spinor notation.
9607753
Anomalous creation of branes
In certain circumstances when two branes pass through each other a third brane is produced stretching between them. We explain this phenomenon by the use of chains of dualities and the inflow of charge that is required for the absence of chiral gauge anomalies when pairs of D-branes intersect.