1. Recycler Injection with Carbon Foils Dave Johnson, Alexandr Drozhdin, Leonid Vorobiev September 8, 2010 Project X Collaboration Meeting

2. Recycler Injection Straight Section Linac: emittance(95%) 2.5  dpop +/- 2 MeV Bunch length 20 mm ( 26 ps rms) Injected beam  = 40 m for this exercise with 3  = 4mm with  adjustable to 10m -> 3  = 2mm Recycler ring lattice  x = 70 m  y = 30 m 3  x = 17.2 3  y=10.7 Recycler rev. period 11.13  s (h=588) beam pulse 10.34  s (546 53 Mhz bunches/turn) Injection beam power 34 kW per injection (2.6E13/injection x 6 = 1.54E14)

3. Recycler Injection HBC1 HBC2 HBC3HBC4 75 to 100 mm 8.941 m 0.606 m 1.068 m Stripping foil H-H- H0H0 H + to inj. absorber Thick foil H 0 ->H + Circulating protons KEK (anti-correlated) H paint V steer Foil orientation (corner foil used in present simulation) Hor. Strip foil (matched to size of beam) 6-8mm 12mm 14mm 18mm

4. Foil Issues Foil Temperature – What is an acceptable maximum temperature? SNS initial camera system designed to measure temps down to 1500-1600 o K but never got a good measurement. A new system is planned…. Best guess for 1.4MW is in the 1500-1600 o K range (M. Plum) JPARC reported on initial tests of measurement system of phototransistor and photodiode. Large errors in photodiode output. Focusing on pulsed measurement. Estimate safe carbon or diamond foil temp around 1600 o K (A. Takagi) Secondary Electrons – Shape and magnitude of magnetic field – trajectory of electrons – beam normal to B – Resistivity of injection foil ( build up of static charge – lesson learned SNS) Minimizing secondary hits by circulating protons – Ring lattice functions ( symmetric insertion, a=0 at foil) – Foil size and orientation (matched to injection beam size) – Painting algorithm Losses due to – H0 excited states (location of foil in rising field of HBC3 only n=1 not captured into circulating beam - 0.7% 2.2 kW will go to injection dump) – Nuclear collision in 500 mg/cm2 foil -> probability 8.3E-6 -> Power=n hits*int/sec*NCP*E*C -> for 30 hits loss approaches 84 W – Large angle coulomb scattering -> previously estimated for 30 hits est. 81 W – H- missing the foil (utilize beam shaping to safely remove large amplitude)

5. Current Investigation Foil type: corner foil (14x18 mm 2 ) KEK painting waveform Program STRUCT: – Implement multiple injections – Time evolution of phase space distributions – Final distribution in x and y – Number and distribution of hits on foil including injected & circulating beam From distribution of hit density, determine foil maximum temperature as a function of injection – Include heating and radiation cooling during each painting cycle – Include radiation cooling between painting cycles – Include energy loss (cooling) from  -electrons that leave foil (MCNPX) Orbit program – Benchmark STRUCT results w/o space charge – Include space charge to determine impact – Include effect of moving circulating beam on/off foil

6. Linac Current/Inj. Time Scenarios ParameterPD IPD IIPX 0I*IIIIIIV (CW) Avg. Linac current [mA]27994211 Inj. Time [ms]1.04331.082.164.2827.72 No. turns/inj9727097 1943852310 No. of injections1136661 Total inj. turns97270582 11642310 325 bunch int.7.8E082.6E081.2E08 5.8E072.9E07 Intensity/turn1.7E125.6E112.5E11 1.3E116.6E10 Intensity/inj1.6E14 2.4E13 1.5E14 Parasitic hits4 3 9 3 --------32/17 2 64/32 2 118/60 2 Foil temp at hottest point1960 1 2100 1880 1 2100 --------- --------1900 4 900 -------- * 2D foil hit distribution plots 1 top number injected beam bottom number added in circulating beam for 1mm inj. beam sigma 2 number of hits for corner foil/estimate for 8mm strip foil 3 using a 6 mm horizontal strip foil 4 Maximum temperature and equilibrium temp at hottest point

7. Distributions during painting Uniform distribution in X and Y Circulating beam hits on foil

8. Proton Driver

9. Hit Density for Corner Foil (1ms) Inj. beam

10. Hit Density for Horizontal Strip Foil

11. Proton Driver Simulations* 1.5E14 per injection (rate 1.5s/10hz) 270 turn 3 ms 90 turn 1 ms Heating dominated by injected beam Dependence on injected beam sigma Project X – Divided up into 6 injections – Longer injection time more circ. Beam hits *J. Beebe-Wang Injected BeamInj+Circ Beam * C-J Liaw

12. Summary For low linac intensity and long injection times the circulating beam hits dominate the interaction with the foil over the injected beam Preliminary simulation of space charge effects during injection appear quite benign at these intensities. Select a favored linac beam current to continue optimization of injection with a foil Need to finish foil temperature calculations Based upon – Parasitic hits – Foil temp Optimize – Foil geometry – Injection beam size – Recycler lattice parameters – Painting algorithm

13. Previous Investigations Proton Driver – 9 mA 3 ms 1 injection – 27 mA 1 ms 1 injection – KEK painting ( Project X – 9 mA 1 ms inj 3 injections – Three painting waveforms KEK Exp (-n/36) and exp (-n/108) sin/cos – Two foil geometries Corner foil Horizontal strip foil

14. Painting Algorithms KEK – Horizontal painting/Vertical steering Exponential – Horizontal painting/Vertical steering Sin/Cos – Horizontal and vertical painting