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Minimum emittance from PSB H- injection

Minimum emittance from PSB H- injection. E.Benedetto Input and discussions with (so far): G.Rumolo , C.Bracco , B.Mikulec , J.B. Lallement. Outline. Minimum emittance from H- injection in PSB (is obtained with no transverse painting) : e L4 + De foil + De sc + De mismatch

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Minimum emittance from PSB H- injection

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  1. Minimum emittancefrom PSB H- injection E.Benedetto Input and discussions with (so far): G.Rumolo, C.Bracco, B.Mikulec, J.B. Lallement

  2. Outline • Minimum emittancefrom H- injection in PSB (is obtained with no transverse painting) : eL4 +Defoil +Desc+Demismatch • Emittance from Linac4 eL4 • Scattering at the foil Defoil • Space charge Desc • Mismatch errors & ripples Demismatch: beta, disp, trajectory, ripples • BCMS beams • Can we measure small beams? • Wire scanners • SEMgrids, MTVs, IPM,… • Transfer between machines

  3. From Linac4 • Emittance (always rmsnormalized) • Nominal Emittance: from source 0.25um • Assuming some blow-up ~0.35um delivered to PSB • Maximum emittance: • Defined by RFQ acceptance = ~0.35um~0.4um to PSB • Intensity (average): • Nominal: from source 80mA • After RFQ, chopper,…  40mA to PSB • Minimum intensity (inside the 0.35um emittance) • We can assume  20mA to PSB From JB Lallement and M. Vretenar’s presentation @ LIU day

  4. Scattering at the foil • Absolute De(depends on b -function and Nh foil traversals): • Number of passages: • 13turns injection(20mA) + ~7 turns KSW decay (remove beam from foil) = 20passages •  cfr. B. Goddard et al.,Proc. IPAC ‘10, Kyoto: Dex, y= 0.25, 0.15 um for 25 hits (carbon 200 ug/cm2)  assume Defoil <~0.20um From Chiara

  5. Space Charge • No machine experience of injecting <1um beams • We should rely on simulations & scaling for the same DQSC • Curve Emittance vs. Intensity with Linac4 • Simulation campaign ongoing • Depends on: • Laslett tune spread • Working point(and resonance compensation) • Injection & painting schemes • Longitudinal parameters • … EB, Chiara, Vivien, Giovanni, Bettina

  6. Mismatch @ inj., kicker ripples, jitters • Ripples in these elements: • Steerers in BI line • KSWpainting bump • BSW (slow chicane bump) constant B field during injection • will induce offset in injected beam (or in the closed orbit)  cfr. In the production of high intensity beams with H- injection, voluntary Dy to increase vertical emittance • or unwanted painting • Need input from hardware • Will be considered in Chiara’s injection simulations Discussion with Chiara and ABT started

  7. Scraping in PSB • Preliminary consideration:reduces Emittance but also Intensity  no gain in brightness • See today production 50ns BCMS beam • (Scraping is after inj. process  i.e. independent of L2 or L4) • Stays on the same curve Emi vs. Int. • Issues (to be studied): • Losses at >160MeV induce higher activation • Scrapers strength at higher energy (Brho & smaller beam size) • Ok! today <8A @65MeV (power supply can go up to 50A) • Precision of scraping such a tiny beam (if we want to get half of ~0.5-0.6um) need studies & maybe MD with LHCPROBE after LS1? From Bettina

  8. Emittance BCMS beam (~half intensity) Assumption with Linac4 “half-of-the-slope” (cfr. Giovanni’s Slide2, 19/7/13), here for the BCMS curve • Production without scraping • Inject half # of turns • Scattering • (~7+7 foil traversals=14 Vs. 20) • Half the SC tune spread • ~same DQ as today @160MeV • Measurements @160MeV confirm no appreciable blow-up over 150ms plateau for today LHC-type beams of 2-3um(MD 4/6/12 by V.Forte, A.Molodozhenstev) • BUT for a smaller (~0.5-6um) beam • No experience • SpaceCharge simulations needed • IF ripples & mismatch at injection are “small”, we could keep the Linac4 emittance + scattering < 0.6um • Again, this is the open point

  9. Can we measure small beams? • No problem with Wire Scanners in PSB and PS • Enough resolution • May be a problem in the SPS… PS @ extraction LHC50#24b_BC…, Ip=388e10 Vertical s=0.714 en=0.65um(?) PSB @ extraction LHCPROBE, I=1.2e10 Vertical s=1.23 en=0.8um

  10. Can we measure small beams? • SEM grids in BTP line are at the limit LHCPROBE en,x=0.6um en,y=0.8um

  11. Transfer between machines • Emittance dilution due to Injection and Dispersion Mismatch are “absolute”, i.e. independent on the initial Emittance (the betatron mismatch is “relative”) • Impact on smaller beams is higher and given by the mismatch factors: • i.e. half the emittance, twice the blow-up in % • Can we still consider it “zero” in our budget?

  12. Summary • Assuming from Linac4: 20mA (min) in 0.4um (max), the emittance at the end of H- injection is ~0.6um (no SC, no ripple, only scattering). • Space-charge and kicker ripples not taken into account in values above: • ONGOING space-charge simulations (emi vs. Intensity curve) • Need input for ripples & mismatch  to be implemented in inj simulations • For BCMS beam, DQSC ~same as today nominal @160MeV • more confident to keep ~0.6um apart from ripples, inj. mismatch and jitters. • Scraping at >160 MeV may be an issue because of activation, and required scraping precision  need study • No problem to measure ~0.7um with FWS in PSB & PS and enough resolution to go down, SEM grids in the line at the limit. • Transfer between machines: • Injection &Dispersion mismatch for smaller beams have a larger impact on emittance dilution. Can we still consider it “zero”?

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