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Recent Progress to Design Helical Cooling Channel

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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Recent Progress to Design Helical Cooling Channel

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  1. MCTF Recent Progress to DesignHelical Cooling Channel Katsuya Yonehara Fermilab APC MC Workshop @ BNL K. Yonehara 1

  2. 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

  3. 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

  4. 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

  5. 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

  6. 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.

  7. 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.

  8. 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

  9. 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

  10. 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

  11. 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

  12. 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

  13. What is next? • Test LiH in normal HCC. • Study low emittance HCC. • Reform MANX to put the RF cell in the magnet.

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