SSC NEWS An electronic mail newsletter about the Superconducting Super Collider Volume 4, No. 4 April 1993 _____________________________________________________________________________ STEADY ADVANCES IN UNDERGROUND CONSTRUCTION As of mid-March, four tunnel boring machines (TBMs) were hard at work in Ellis County. Proceeding clockwise from N15, the first of the Collider tunnel segments under construction extends from N15 to N20, a stretch of 2.7 miles through shale. The construction subcontractor, Obayashi/Dillingham, had bored 1164 feet of this segment by March 18, measuring from the centerline of the Magnet Delivery Shaft. Best daily progress to date was 70 ft/day. (Ultimate goal: 150 ft/day.) The next segment, N20 to N25, another 2.7 miles extending partly through shale and partly through chalk, is being excavated by Traylor Brothers/Frontier Kemper; they reported 551 feet completed by March 18. More importantly, their "productivity slope" continues to be positive. The best news comes from N25 to N40, an 8-mile segment extending through chalk only. Gilbert/Shea reports 5055 feet (1 mile) completed, well ahead of schedule. Their best advance rate to date is 266 ft/day. Boring through the chalk is not without problems, however, in that the chalk dust is proving too fine to be controlled by the filtering system in place; other methods are being tried. At N40, meanwhile, another TBM of Gilbert/Shea has been all set to commence boring the N40 to N55 segment for some time, but has been delayed by a missing piece of "tail shield." The TBM finally got going on March 16. At N45, the last shaft (personnel shaft) was completed as well. In the south arc, surface preparations have been completed at S40, and work is under way on both the magnet delivery shaft and ventilation shaft. The actual boring of the S40 to S55 8-mile tunnel segment by Traylor Brothers/Frontier Kemper awaits arrival of their TBM at N25 in the north arc. In the west complex, meanwhile, construction is more obvious to the onlooker. Underground construction for the Linac tunnel and beam transfer line to the LEB is essentially completed, and the 800-foot-long RF gallery on the surface is well along, as are the ion source building and various utilities. At the site of the Low Energy Booster slightly to the north, surface preparations are all but completed, with cut-and-cover underground excavation of the ring and its beam lines under way. The contractor here is Cajun Contractors of Baton Rouge, Louisiana. A portion of the MEB tunnel to be excavated under the same contract is well along, as is the LEB-to-MEB transfer tunnel, and a portion of the LEB tunnel proper. Construction of the Industrial Road to the west , and site preparation work in the east complex at IR 5 and IR 8 south of Palmer, as well as on the East Complex Connector Road, continues at a pace dictated by the erratic Texas weather. VACUUM R&D ACTIVITIES AT SSCL In-house vacuum R&D at the Laboratory involves a number of individuals within PMO, ASD, and MSD, under the leadership of W.C. Turner. Outside institutions involved in this work include Los Alamos, CEBAF, Virginia Polytechnic, and especially UT-Arlington, Brookhaven, and the Budker Institute for Nuclear Physics at Novosibirsk. Much progress has been made in this technical area during the past year, the highlights of which may be summarized as follows. A vacuum laboratory is now in operation at the Central Facility. Warm and cold photodesorption experiments have been under way at BINP for some time, and similar measurements are in the pipeline at Brookhaven. (These follow up on much earlier photodesorption experiments by the SSC Central Design Group in the mid-80s.) Recent results indicate that room-temperature photodesorption is only weakly dependent on the presence of a magnetic field--good news from the experimenter's point of view--and that photodesorption coefficients at 80 K and 4.2 K are much lower than at room temperature (a finding at variance with older CDG results). However, the recycling of small amounts of cryosorbed gases appears to be a serious concern and is the focus of ongoing 4.2 K photodesorption experiments. A design effort for a prototype 80 K vacuum tube liner is nearly complete, and numerous measurements and simulations of liner impedances have been made. Alternative beam tube materials are also under investigation at SSCL, as well as at UTA, VPI and at BNL. Distributed pump designs are under way at SSCL and at CEBAF. More generally, an ongoing broad program is investigating Collider beam tube options involving 4.2 K with and without distributed pumping and 80 K/20 K systems with distributed pumping. CRYOGENIC UPDATE AT N15 No fewer than four helium refrigeration plants are associated with the N15 service area at the northern end of the west complex in Ellis County. The first of these plants to be commissioned was the "Plan B" refrigerator of 500 watt capacity. It cooled the ASST string test for its milestone run last summer, and again for a second run that ended this February. It has been decided to relocate this plant to the Central Facility, where it will be used in the testing of spool pieces. First tests are earmarked for late June of this year. Two much larger helium plants are being installed at N15, and a third will be coming. All three will have essentially the same refrigeration capacity, sufficient to cool one of the 8-km-long cryogenic sectors of the Collider ring. The first of these plants, the Plan A refrigerator, has already been operated successfully, and final acceptance was expected by the end of March. It will be used for the next phase of the ASST: a full cell involving 10 dipoles and 2 quadrupoles. The second helium plant, dedicated to the Magnet Test Laboratory (MTL), should be fully installed by the end of May. (The MTL will have 11 stands for sequential testing of individual magnets.) A third refrigeration plant, known simply as the N15 plant, has not yet arrived. The third plant and the Plan A refrigerator will be interchangeable, and either can be employed in cooling the local cryogenic sector extending north and south from N15. Meanwhile, an RFP for the procurement of 11 Sector Refrigerator Surface Systems was issued some time ago. Bids were due March 17. Each system will contain a helium refrigeration subsystem, compressors, liquid and gaseous helium storage facilities, and a surface distribution box. They will interface with the same number of Shaft and Tunnel Systems, whose procurement packages are in preparation. These systems will contain a cold compressor, shaft and tunnel transfer lines, a nitrogen subcooler, and a distribution box. SSCL LIBRARY FACTOID It may come as a surprise to some, but the SSCL Library currently has approximately 5,000 books in its collection, with another 1,000 on order. In addition, it subscribes to 570 journals, magazines, and newspapers. Among the newspapers, aside from the various local newspapers, are The New York Times, The Washington Post, The Austin American Statesman, USA Today, The Wall Street Journal, Barron's, Le Monde, and The Japan Times. MEDICAL PROTON THERAPY AT THE SSC One of the most promising on-site spin-offs of the SSC is likely to be a facility for proton beam treatment of various malignancies, using the SSC's Linac as the source of protons. In its normal operation, the Linac idles for more than 60% of the time waiting for the next accelerator in the SSC injector chain, the Low Energy Booster (LEB), to be ready to accept another charge of protons. During the idle periods, the Linac could provide protons for such a medical irradiation facility. The sponsor of the potential facility is the University of Texas Southwestern Medical Center in Dallas, whose spokesman is Dr. Eli Glatstein, chairman of UT Southwestern's Department of Radiation Oncology. The project has been under scrutiny for some time, with active participation of Aquirre Associates, Inc., Lawrence Berkeley Laboratory, the Particle Accelerator Corporation, and the SSCL. Several technical schemes have been reviewed, and a conceptual design and detailed cost estimate have been made. The facility would be located near the injectors in the SSC west complex. Protons of the appropriate doses and with energies ranging from 70 MeV to 250 MeV would be delivered from the Linac without in any way compromising the accelerator's primary function as an injector. The protons would be extracted beyond the Linac tunnel enclosure, at the beginning of the beam transfer tunnel to the LEB. They would then pass to the therapy facility, which is visualized as having one or two levels underground and one at ground level. The subterranean levels would feature two shielded treatment rooms with associated patient preparation and examining rooms. The surface level would house office and reception spaces and various laboratories with facilities for diagnostics and testing of patients. The underground conventional construction for the Linac, which is already completed, provides a beam extraction stub for this very purpose. A comparable dedicated proton beam treatment facility is at the Loma Linda University Medical Center in California, which uses a 250-MeV proton synchrotron constructed for the purpose by Fermilab. Fermilab also operates a neutron therapy facility in its accelerator complex in Batavia. The Harvard cyclotron laboratory is the home of a pioneer among proton treatment facilities--a facility still in operation. SSC STATUS REPORT The laboratory has now completed the preparation of a 60-page status report through 1992. It also covers some major developments that have occurred recently on the project and within the physics program. The topics are discussed in the context of the overall construction of the SSC facilities and the fabrication of technical components. The booklet includes many photographs that illustrate the progress that has been made over the past couple of years. It is hoped that this report will be widely read by the entire high energy physics community and by a broad range of individuals concerned about the building of the new laboratory. The Super Collider Status Report was drafted by the people carrying out the work, but it is not overly technical and is being distributed to employees of the Laboratory and other interested parties. A broad mailing outside the laboratory will begin in early April, and should be completed by April 9. A limited supply of additional copies will be available through the Office of External Affairs which will oversee their distribution. DATES TO REMEMBER May 3-5, 1993 First European Workshop on Beam Instrumentation and Diagnostics for Particle Accelerators Montreux, Switzerland (Ch. Parthe, CERN: 41-22-7674619) May 5-8, 1993 International Industrial Symposium on the Super Collider (IISSC) San Francisco, CA. (P. Patterson: 619-490-0164) May 17-20, 1993 1993 Particle Accelerator Conference Washington, D.C. (A. Quarrie: 804-249-6377) May 31-June 4, 1993 Physics Computing '93 Albuquerque, NM (Executive Secretary, American Physical Society) June 1-3, 1993 International Symposium on SSC Physics and Detectors Joint Institute for Nuclear Research, Dubna (By invitation only.) (K. Anderson, SSCL: 214 708-1040) June 16-18, 1993 XIII Int. Conf. on Physics in Collision Univ. of Heidelberg (Conf. Secretariat: 49-6221-564332) June 21-July 2, 1993 Workshop on Beauty Physics at Proton Accelerators Snowmass, CO (V. Luth, SSCL and J. Appel, Fermilab) SSCLAB CALENDAR To see a longer list of HEP events, including SSC detector collaboration meetings, log onto SSCVX1 as SSCLAB (no password is required) and select calendar from the menu. Send any comments or items for the calendar to USERSOFFICE@SSCVX1. HOW TO SUBSCRIBE TO SSC NEWS Send a one-line mail message to: LISTSERV@UTARLVM1 (that's LISTSERV, not SSCNEWS). The full Internet address is: LISTSERV@UTARLVM1.uta.edu The message should be similar to the following example: EXAMPLE: SUB SSCNEWS Heike Kamerlingh Onnes (Insert your own name, using Initial Capital letters) LISTSERV will pick up your email address from your message. To unsubscribe, send SIGNOFF SSCNEWS. If your email address changes, please sign off from the old account and then subscribe from the new account. Send any suggestions or questions to Per F. Dahl: DAHL@SSCVX1.