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MCTF. Recent Progress to Design Helical Cooling Channel. Katsuya Yonehara Fermilab APC. 1. Targets in this talk. The final HCC design is still on going. But I will show some simulation results which may indicate some clues to breakthrough some crucial issues: End-to-end HCC design
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MCTF Recent Progress to DesignHelical Cooling Channel Katsuya Yonehara Fermilab APC MC Workshop @ BNL K. Yonehara 1
Targets in this talk The final HCC design is still on going. But I will show some simulation results which may indicate some clues to breakthrough some crucial issues: • End-to-end HCC design • Combining RF section in HCC will be discussed. • It strongly relate with pre-cooler design. • What’s next? 2
Simulation in ideal condition RF is completely inside the coil. • Use a pillbox cavity (zero-thickness window this time). • RF frequency is determined by the size of helical solenoid coil. v ~ 0.97 c at 200 atm GH2 • To realize practical condition: • The pressure of gaseous hydrogen is 200 atm at room temp to • realize the practical RF field gradient. • The operation temperature in an absorber container • can be low, i.e. LN2 temp. • Required gap between a coil and a RF cell is 20~30 mm which • includes supports, a cell wall, and a thermal isolation shield. • Additional space is needed for a RF feed line (20~25 mm). • Pressurized wall is needed (it may be an outer shell of channel). GH2 Window RF cavity Helical solenoid coil 3
Cooling simulation in ideal HCC Start point HCC goal • There is a missing link between a start point • and an acceptance of 1st HCC. • A pre-cooler is needed (following section). • We need to occupy another missing link at • lower emittance. • The transmission efficiency is 50 %. • Caused by a transverse mismatching in • between HCCs. • This can be improved by using a smaller • frequency step. 4
Conceptual picture of pre-cooler (design-1)based on MANX channel • HCC section: • kappa = 1.0 • lambda (m) = 1.6,1.2,1.0,0.8… • No RF • Small coil gap to make an ideal field • Filled with LH2 HCC section RF section HCC section RF section HCC section • RF section: • kappa = 1.0 • lambda (m) = 1.6 • Large coil gap to put the RF cavity • Filled with GH2 • Gas pressure = 100 atm @ 300 K, • This scheme can relax some problems caused by a pressurized gas. I stacked this design. Problem is caused by the mismatching in longitudinal phase space. Magenta: RF coil Red: RF cavity Yellow: HCC coil 5
Momentum-time phase space advance in design-1 cooling section with three different field configurations Geometric parameters: l=1.6 m, k=1.0, LH2 absorber Two clear indications • HCC can be more isochronous by tuning the dispersion. • However, it makes less longitudinal phase space cooling. dp slope gets smaller at stronger isochronous condition.
Problem in RF section • (top layer) dp-dt in 0-crossing RF • (bottom layer) dp-dt in 100 atm GH2 RF l=1.6 m, k=1.0, Erf = 20 MV/m, jrf = 150 degree The phase advance in HP GH2 RF is asymmetric. This causes mismatching. We need further studies or it may not be the best choice for pre-cooler.
Conceptual picture of pre-cooler (design-2) • Put RF cavity in between coils. • Required gap can be 100 mm. • Thermal isolation+supports+cell wall… Upstream Matching HCC Downstream Matching • Gap between coils = 0.04 m • Current = 1075.0 A/mm2 Pressurized wall LHe RF cavity Helical solenoid coil (SC or HTSC) m beam GH2 Window (Be) Track of reference particle 8
Using LiH absorber in design-2 pre-cooler • kappa = 1.0 • lambda (m) = 2.0 m • helical radius = 0.32 m • inner coil radius = 0.33 m • coil thickness = 50 mm • GH2 pressure = 100 atm • LiH thickness = 2.0 mm • Erf = 40 MV/m, jrf= 153 degree • frf = 325 MHz • RF length = 100 mm LiH coil GH2 GH2 filled RF cell RF cell is invisible in those pictures. LiH GH2 coil
Simulation result in design-2 pre-cooler • Wiggler at beginning is happened by • mismatching and statistic error. • Reaches the equilibrium at z=30 m. • 6D cooling factor is 8 which is slightly • smaller than the previous simulation result. • This may be caused by LiH. • Design-2 pre-cooler completely satisfies • the initial gap. HCC goal
Apply MANX channel for pre-cooler • Do MANX experiment to test 6D theory and validity of simulation. • Helical solenoid coil is designed a segment structure to generate tapered field. • Probably we can replace some segments to a RF cell. 11
A pre-cooler design has been investigated. Design-2 seems to be better than design-1. 6D cooling is demonstrated in LiH channel. MANX can be used as a pre-cooler by re-forming helical coils and put RF cells in between coils. Conclusions 12
What is next? • Test LiH in normal HCC. • Study low emittance HCC. • Reform MANX to put the RF cell in the magnet.