Buncher-System for FRANZ

Transcription

1 Buncher-System for FRANZ Concept Beam-Dynamics Chopper-System

2 Buncher-System for FRANZ 150 kv Terminal Wb = 120 kev Pb = 2.4 x 104 W Wb = 1 MeV Pb,max = 1 x 104 W Wb = MeV Pb,max = 2.1 x 104 W Rebuncher Steerer RFQ Ionenquelle Chopper t = ns f = 250kHz Strahlstopper Detektor- und Komponententeststand CH Rebuncher Bunchkompressor Chopper f = 5-10MHz Dipolmagnet 7 Li Target parameters at the Lithium-Target: (Bucher-System for FRANZ: Riezlern)

3 Pulse-Structure after the DTL 175MHz-DTL rep.rate = 250kHz 4µs E ~ 2.0MeV 50ns Macro Bunch Micro Bunch 100ns

4 Pulse-Structure after the DTL 175MHz-DTL rep.rate = 250kHz 4µs E ~ 2.0MeV 50ns Macro Bunch Micro Bunch 100ns

5 Concept Inspired by [Phys. Rev. 88(2), (1951)] a 1ns-Buncher-System composed of a rf-chopper and two skew magnets with spatial nonconstant magnet fields is proposed. Chopper f < 10 [MHz] Protons T = 50[ns] rep.rate = 250[kHz] E = [MeV] Imax = 200[mA] Idea: About 7-9 micro bunches be deflected on different paths Arrive at the same time at the target Dipole-Magnets B = [T] Neutrons Advantages of two skew magnets: More parameter to manipulate the beam dynamics Greater distance between the bunches More compact geometry (at the sample) T = 1[ns] rep.rate = 250[kHz] E < 500[keV] Flux ~ 107[ cm-2s-1)] Li-Target 7

6 Trajectories Cartesian coordinate system Parameters: α, Ω, d, e, L α/2 L Ω/2 d e

7 Trajectories w1 b w2 Cartesian coordinate system Parameters: α, Ω, d, e, L w1(α, Ω, d, e, L) w2(α, Ω, d, e, L) b(α, Ω, d) --> R, B

8 Bunch-Interaction N = total #bunchs (7 to 9) j = #bunchs k = #iteration

9 Bunch-Interaction N = total #bunchs (7 to 9) j = #bunchs k = #iteration j t time-axis i k-1 k k+1

10 Bunch-Interaction Bunch.Nr. x[m] e e e e e e e e e+00 y[m] 8.000e e e e e e e e e-02 v_x[m/s] 1.901e e e e e e e e e+07 v_y[m/s] e e e e e e e e e+06 alpha[deg] alpha[rad]

11 Bunch-Interaction

12 Bunch-Interaction

13 Bunch-Interaction

14 Bunch-Interaction

15 Bunch-Interaction

16 Bunch-Interaction

17 Bunch-Interaction

18 Bunch-Interaction βλ = 0.111[m] <=> T = 5.7[ns] y = 0.006[m] x = 0.030[m] <=> t=1.5[ns]

19 Bunch-Interaction

20 Bunch-Interaction

21 Beam-Dynamics Available Parameters: 2 edge angle, rf-voltage TRACE3D PARMILA( SCHEFF ) Envelope Space-charge calc.: - approximation: electrical field of an uniformly charged ellipsoid Multi-Particle Space-charge calc.: - PIC - radiale Symmetry - 2D-Solver ( r, z ) =>improper for transport through dipole! First order estimation for Envelope => fast calculation PARMILA( PICNIC3D ) Multi-Particle Space-charge calc.: - PIC - grid: 3.5*(X/Y)_rms - gauß distributed charges on gridpoints - 3D-Solver => more accurate output

22 Beam-Dynamics TRACE3D-Input Twiss-Parameter

23 Beam-Dynamics V_g=100[kV] (8 ; 25) (25 ; 8) PARMILA(PICNIC3D): I=200[mA],10000 [particle], 100[calls/m]

24 Beam-Dynamics (-8 ; 20 ) (20 ; -8) V_g=400[kV] PARMILA(PICNIC3D): I=200[mA],10000 [particle], 100[calls/m]

25 RF-Gap: Config1 Mikro-Bunche Protons T = 50[ns] rep.rate = 250[kHz] E = [MeV] Imax = 200[mA] Chopper f<10 [MHz] i-1 i i+1 α Dipole-Magnets B = [T] 0.4[m] RF-Gap Neutrons (at the sample) T = 1[ns] rep.rate = 250[kHz] E < 500[keV] Flux ~ 107[ cm-2s-1)] 7 Li-Target

26 RF-Gap: Config2 Protons T = 50[ns] rep.rate = 250[kHz] E = [MeV] Imax = 200[mA] Mikro-Bunche Chopper f<10 [MHz] i-1 Dipole-Magnets B = [T] i i+1 RF-Gap Neutrons (at the sample) T = 1[ns] rep.rate = 250[kHz] E < 500[keV] Flux ~ 107[ cm-2s-1)] 7 Li-Target Smaller aperture than Config1 Gap-Geometry => transversal and longitudinal focussing per bunch!

27 Chopper-System Electrical Deflector: Electro-magnetic Deflector: E(t), capacitor LC-oscillator sine-pulse B(t), dipole with ferritic yoke ( J.-C. Sun) triggering by high-voltage-switchs variable pulse(!) Pro: technical realisation Pro: no Energy-shift max. deflection independent from gap (!) pulse-repetition ~ 250[kHz] (!) Contra: longitudinale Energy-shift(?), first estimation without fringe-fields max. deflection<=> Gap (!) max. deflection<=> E_max, sparking(!) f > 5[MHz], air-coil(!) rf-amplifier skin-effekt EM-radiation Contra: material costs Ferrite: small gradient, B_max (!!) technical realisation of the trigger-system eddy current, powerloss

28 Chopper-Frequency (el.deflector) 50ns 9 Bunche => 1/2 T : 9 Bunche => 1/4 T :

29 Chopper-Frequency (el.mag.deflector) 50ns

30 Chopper-Frequency (el.mag.deflector) 50ns Max. performance factor(f *B_max/[Hz T]) at PV=500[mW/cm^3] <=> 100[ C]: 80[kHz T]:

31 TO DO Beam-Dynamics LORASR, dispersion function, achromate design Twiss-paramters and emittances after Chopper [ E(t), B(t) ] Chopper effect of fringe fields for both chopper concepts, energy shift due to the el.chopper E_max, B_max RF-Gap (LINAC-AG) design optimisation