Circulating Electron Bunches without a Circulator Ring Proposed
Circulating Electron Bunches “without” a Circulator Ring
Proposed Technology Validation Tests (Douglas) • By-pass – Test bunch train transfer • RF separator &/or kicker based • Test longitudinal match – De-chirp/rechirp • CSR benchmarks – MBI/LSC/CSR – Some tests now in progress
Circulator Ring With ERL (Hutton) Need a bypass beam line (can use the UV beam line? ) Can arrange circulation of the beam, need two kickers Can do energy recovery Passes the SRF linac in each turn, may have a repeated 2) / rechirp/dechirp effect 3π r 2 o • Complex longitudinal gymnastics / π • • After turns Phase before entry of linac In linac 0 0 Acceleration 1 π+π/2 “Chirp” 2 2π+π/2 “Dechirp” 3 3π+π/2 “Chirp” 2 k-1 (2 k-1)π+π/2 “Dechirp” 2 k kπ+π Deceleration 0) se= = se pha a ph ng ( =π) ( i e it on ross has ra o-c (p e l ce zer tion )λ c 2 : a a / s: sses eler +1 s k a ( c p pa de : t e s e : l r c Fi idd ass en r p e M st iff a d L h gt n le h t Pa Kicker kicker
Circulator Ring Using IR & UV Lines (Nissen) Dechirper Kicker arc Kicker Rechirper arc • Moves the beam forward through the IR beamline and backward through the UV beamline. • Needs two 180 degree arcs and a set of kickers • Does energy recovery
David Douglas’s Comments • Extremely clever topology. • Yes, that would work. One could also do the exchange at a single point mid-IR (say in the vicinity of the optical cavity chicane) and use a single kicker to eject the bunch, then fire again to inject another bunch later on. This leaves space for injection/extraction transport and cuts down on cost.
System Layout recirculation/decompression transport CCR cooling solenoids dechirper beam exchange system dump ERL rechirper injector recovery/recompression transport
Circulator Ring with a Bypass of Linac (Li) Kicker (to dump) Kicker (to dechirp bypass) Kicker (into circulator ting) Main circulating beam line dechirp Bypass beam line for dechirp Kicker (out of dechirp bypass) • • • Circulator ring beam line does not include the SRF linac. Need a bypass beam line for dechirping No energy recovery. Should be OK for test bed (if beam power is less than 90 k. W). Can add energy recovery if passing the dechirp beam line for 2 nd time (and right phase) Need four kicker • • • e-bunch from the injector is accelerator by the SRF linac and also gained an energy chirp e-bunch is kicked into the circulator beam line, passing through the 180° bend for increasing bunch length e-bunch is kicked in and out the UV beam line for de-chirp e-bunch goes up to 100 rounds in the circulator ring Finally e-bunch is kicked into the beam dump
Maximum Allowable Current without ERL • • • Estimate of dump capacity: 9. 1 m. A x 9 Me. V (injector energy) = 81. 9 k. W Circulator ring evolution frequency: (3 x 108 m/s) / (150 m) = 2 MHz Current of one bunch in the ring: (125 p. C) x (2 MHz) = 0. 25 m. A With 50 Me. V electron energy, beam power is 12. 5 k. W Total bunches allowed in circulator ring: 81. 9 k. W / 12. 5 k. W ~ 6. 5 bunches Bunch charge Beam energy n. C Me. V 0. 125 54 0. 125 Bunches in circulator ring Bunch spacing Beam current Beam power m m. A k. W 6 25 1. 5 81 25 12 12. 5 3 75 0. 25 54 3 50 1. 5 81 0. 25 25 6 25 3 75 0. 5 54 1 150 1 54 0. 5 25 3 50 3 75
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