THE AGS-BASED SUPER NEUTRINO BEAM FACILITY CONCEPTUAL DESIGN REPORT
After more than 40 years of operation, the AGS is still at the heart of the Brookhaven hadron accelerator complex. This system of accelerators presently comprises a 200 MeV linac for the pre-acceleration of high intensity and polarized protons, two Tandem Van der Graaffs for the pre-acceleration of heavy ion beams, a versatile Booster that allows for efficient injection of all three types of beams into the AGS and, most recently, the two RHIC collider rings that produce high luminosity heavy ion and polarized proton collisions. For several years now, the AGS has held the world intensity record with more than 7 x 10{sup 13} protons accelerated in a single pulse. The requirements for the proton beam for the super neutrino beam are summarized and a schematic of the upgraded AGS is shown. Since the present number of protons per fill is already close to the required number, the upgrade is based on increasing the repetition rate and reducing beam losses (to avoid excessive shielding requirements and to maintain activation of the machine components at workable level). It is also important to preserve all the present capabilities of the AGS, in particular its role as injector to RHIC. The AGS Booster was built not only to allow the injection of any species of heavy ion into the AGS but to allow a fourfold increase of the AGS intensity. It is one-quarter the circumference of the AGS with the same aperture. However, the accumulation of four Booster loads in the AGS takes about 0.6 s, and is therefore not well suited for high average beam power operation. To minimize the injection time to about 1 ms, a 1.2 GeV linac will be used instead. This linac consists of the existing warm linac of 200 MeV and a new superconducting linac of 1.0 GeV. The multi-turn H{sup -} injection from a source of 30 mA and 720 {micro}s pulse width is sufficient to accumulate 9 x 10{sup 13} particle per pulse in the AGS[10]. The minimum ramp time of the AGS to full energy is presently 0.5 s; this must be upgraded to 0.2 s to reach the required repetition rate of 2.5 Hz. The required upgrade of the AGS power supply, the rf system, and other rate dependent accelerator issues is discussed. The design of the target/horn configuration is shown. The material selected for the proton target is a Carbon-Carbon composite. It is a 3-dimensional woven material that exhibits extremely low thermal expansion for temperatures up to 1000 C; for higher temperatures it responds like graphite. This property is important for greatly reducing the thermo-elastic stresses induced by the beam, thereby extending the life of the target. The target consists of a 80 cm long cylindrical rod of 12 mm diameter. The target intercepts a 2 mm rms proton beam of 10{sup 14} protons/pulse. The total energy deposited as heat in the target is 7.3 kJ with peak temperature rise of about 280 C. Heat will be removed from the target through forced convection of helium gas across its outside surface. The extracted proton beam uses an existing beamline at the AGS, but is then directed to a target station atop a constructed earthen hill. The target is followed by a downward slopping pion decay channel. This vertical arrangement keeps the target and decay pipe well above the water table in this area. The 11.3 degrees slope aims the neutrino beam at a water Cerenkov neutrino detector to be located in the Homestake mine at Lead, South Dakota. A 3-dimensional view of the beam transport line, target station, and decay tunnel is provided.
- Research Organization:
- BROOKHAVEN NATIONAL LABORATORY (US)
- Sponsoring Organization:
- DOE/OFFICE OF SCIENCE (US)
- DOE Contract Number:
- AC02-98CH10886
- OSTI ID:
- 15009972
- Report Number(s):
- BNL-73210-2004-IR; R&D Project: PO-22; KA-04-01; TRN: US0407264
- Resource Relation:
- Other Information: PBD: 8 Oct 2004
- Country of Publication:
- United States
- Language:
- English
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