HCC Magnet Future Plans Steve Kahn Aug 9, 2008

1. HCC Magnet Future PlansSteve KahnAug 9, 2008 NFMCC Friday Meeting S. Kahn -- HCC Magnet Plans

2. HCC Magnet Phase II Work Plan • Develop the concepts and engineering designs of HCC systems with Helical Solenoid magnets with special emphasis on HTS applications with the highest possible field. • Helical Solenoid concepts will be developed to incorporate RF cavities for a practical HCC design. • Simulations to optimize and verify muon cooling behavior of HCC engineering designs. S. Kahn -- HCC Magnet Plans

3. Parameters Describing the HCC Cooling Channel Current Parameters for HCC Used for the RF in HCC Used for High Field Magnet R&D Previous HCC Parameters on which the proposal was based. S. Kahn -- HCC Magnet Plans

4. High Fields for Helical Solenoid Applications • Concentrate on the developing highest field HCC segment. • Requiring 17 T field on the reference orbit which gives 23 T at the conductor. • Investigate the suitability of HTS conductors, particularly Bi-2212 and YBCO. • Performance in an anisotropic field is important. The HCC will exhibit both Br and BZ components at the conductor. • Bi-2223 and YBCO tapes have previously shown a strong dependency of JE on the direction of the field. • Having the field in the plane of the conductor is more desirable. • Bi-2212 round cable is not sensitive to field direction. • Recent development has shown that doping of YBCO conductor can reduce this field anisotropy at 77°K. We are interested in 4.3°K • Develop, build and test hybrid four coil test model. • HTS insert and Nb3Sn outsert arrangement. (see next transparency) S. Kahn -- HCC Magnet Plans

5. Fig. 6: An example of a hybrid coil arrangement where the inner coils are made of HTS conductor and the outer coils are made of Nb3Sn conductor. Hybrid Coil Arrangement Nb3Sn Outsert HTS Insert S. Kahn -- HCC Magnet Plans

6. Hybrid 4-Coil Test • For each of the coils described previously ~3 T of the field comes from the HTS. • Each of these coils requires about 200 m of 0.8 mm Bi-2212 cable. (Cost of Bi-2212 is ~$20/m giving $20K in fuzzy math). • A four coil test with these coils would only produce about half of the desired field. As such this may not be a realistic mechanical test. • We would like to explore adding sufficient additional HTS conductor to achieve a more representative field. • I still need to do calculations to determine what is needed. S. Kahn -- HCC Magnet Plans

7. RF Cavity Primary Helix Coil Bucking Solenoid Coil Helical Quadrupole Correction Coil Incorporation of RF into the HCC Channel • Integrate 400 MHz cavities into HCC using the anti-solenoid and correction coil scheme. • As we learned from Valeri Balbekov lower frequencies are more desirable for the HCC. • 400 MHz is at the edge of being stable for segment 1 parameters. 200-300 MHz would be more preferable. • Allowing clearance for H2 containment vessel, thermal isolation and coil support. S. Kahn -- HCC Magnet Plans

8. Coil Size vs. Cavity Size • Lower frequency RF cavities require more radial space. • To replace the dE/dx losses from 400 atm (RT) H2 gas, we must have a real estate gradient of 32 MV/m at 140º phase. • This suggests that we need to put the cavities inside the coils. • The other alternative is to lower the gas pressure and increase the channel length. (Scheme 2). • Increasing the coil radius has an effect on field components and their derivatives. • The figure shows BZ, B, dB/dr and dB2/dr2 as a function of coil inner radius. • This is why we need the correction coil scheme seen previously. Frequency vs. Radius for Pillbox Cavities S. Kahn -- HCC Magnet Plans

9. Space Considerations are Essential to RF Incorporations • Radial space clearance imposes constraints on the RF frequency on enclosed cavities. • Upper figure illustrates an estimate of the radial budget as previously recommended by the TD. • Reducing the clearance requirements would be beneficial. • Using Inconel 718 instead of SS 316. Can reduce 1.25” to 1 cm. • Reduce coil support. • All forces are radially outward. • RHIC magnets did not require this level of coil support. • Use same pressurize of N2 gas to cool cavities. Eliminate the pressure difference on the containment vessel. S. Kahn -- HCC Magnet Plans

10. Technical Feasibility of Helical Cooling Channel Magnet System. • Develop concepts and engineering designs for HCC using helical solenoid magnets. Emphasis should be put on using Nb3Sn conductor for medium field HCC and HFS conductor for the high field HCC. • Investigate using “hybrid model” using HFS insert inside of Nb3Sn outsert to construct HCC for the high field segment. (Part of Muons Inc./FNAL phase II proposal). Build four coil test model of high field hybrid model. • Study the effects of anisotropic field on the current density of YBCO conductor at 4.3ºK. Investigate whether doping YBCO conductor can alleviate the anisotropic field response to the conductor current density. • Investigate how to incorporate RF into the helical cooling channel magnet system. Study what changes need to be made to accommodate the RF. (Part of Muons Inc/FNAL phase II proposal.) Study the “correction coil” approach as a possible solution. Build and test a short HCC with RF cavities imbedded. This would be and engineering test experiment with several cavities and coils. • Test “hybrid model” coils in linear (non-HCC) configuration to see how high a field can be obtained. • This program should be part of the 5 year plan. S. Kahn -- HCC Magnet Plans