Cryogenic Experts Meeting (19 ~ ) Cooling scheme discussion for 300 Tm High Energy Beam Transfer line (HEBT) with large inclination MT/FAIR – Cryogenics Y. Xiang, M. Kauschke

Design constraints to helium flow in 300 Tm HEBT due to the tunnel with large inclinations; Simulation results on flow pattern analysis of two- phase helium flow in 300 Tm HEBT as the baseline design in FBTR; The single phase helium cooling scheme is to be presented together with one of the current feeding concepts; Conclusions Outline Cryogenic Experts Meeting (19 ~ )

300 Tm HEBT layout HERA type quadrupole HERA / UNK type dipole

Constraints given by the inclined tunnel for extraction One of the major constrains for magnet string design and layout; Inclination up to 6.6  (11.5%, 115 mrad ) for 300 Tm HEBT from SIS 300 to beam dump and CBM No such a big slope has ever been considered as constraints in the superconduting magnet baseline design for the existing large machines, e.g., HERA ring (6.3 km)  (1 %, max 10 mrad) LHC ring (27 km)  (1.4 %, 14 mrad) Tevatron (6.0 km), RHIC (3.8 km), Nuclotron (251.5 m) --- nearly horizontal Upper limit for using wheeled-vehicles for magnet installation % (2.3 , statement from Fermilab, "Design Study for a Staged Very Large Hadron Collider", 2001)

Design constrains to helium flow in magnet string with large inclinations One of the design experiences for two-phase helium flow in HERA proton ring: The JT expansion is done at the lowest point of each octant of HERA so that the two-phase flow in HERA magnets is always directed uphill to avoid the capture of bubbles. One-phase and two-phase helium flow arrangement (baseline design in FAIR Baseline Technical Report 2006)

Two-phase helium flow pattern in the inclined part of 300 Tm HEBT from SIS 300 to Beam Dump Too close to the transition boundary which means high risk of changing into unstable flow pattern We need another concept of cooling scheme!

Studies at CERN in A Possible Upgrade of the LHC Injection Lines (450 GeV) to 900 GeV using HERA Dipoles Injection lines between SPS and LHC are, TI2 (2.9 km with up-hill and down-hill slopes) --- steepest slope is 2.6%; TI8 (2.7 km) --- steepest slope is 3.77% One statement of the study, "The lines are characterized by a strong inclination (7.2% max slope)... The distribution to the magnets of liquid helium in strongly inclined channels and over a distance of several hundred meters represents a considerable cryogenic challenge." Such a study lets people to trace back another study which was done at CERN in earlier 1993 :

Single phase cooling schemeAlternative two-phase cooling scheme Studies at CERN in Design Criteria of the cryogenic system for the CERN LHC injection lines The authors proposed two cooling schemes for the inclined injection lines: Only the gaseous stream flows into a pipe thermally insulated from the existing channel Two single phase streams flow in a thermally insulated pipe inside the existing two channels to prevent possible heat transfer between forward and return streams Statements of the Study at CERN in 1993 : "The single phase cooling scheme adopts a cooling method different from that already operated in HERA. The alternative two-phase cooling scheme offers the possibility of developing a new challenging cooling scheme for SC magnets with two-phase flow over very long distances in strongly inclined channels. However, since it introduces several unknowns and “its feasibility is still doubtful”. Further tests are required before the solution can be seriously pursued."

Single phase helium cooling scheme for 300 Tm HEBT

Flow scheme of current feedbox for superconducting links (DFBL) for LHC If the concept that the current feedboxes are located close to the feeding points of the magnet string (LHC mode) inside the extraction tunnel is not a favourite solution for the power supply requirement at GSI, the recooler has to be integrated in the magnet cryostat design. No clear picture on this point at GSI up to now because of the uncertainty of cold link design.

Conclusions The numerical simulation shows the baseline of two- phase cooling flow scheme specified in FBTR for the 300 Tm HEBT magnet strings with strong inclinations has high uncertainty. The single phase cooling scheme which is based on the concept initiated at CERN for LHC injection lines has been presented for the 300 Tm HEBT magnet string. To start the recooler design, one needs the final decision of current feeding concept. Cryogenic Experts Meeting (19 ~ )