Machine Design Options for LEP3, TLEP & SAPPHiRE
Frank Zimmermann2nd LEP3 Day, 23 October 2012
work supported by the European Commission under the FP7 Research Infrastructures project EuCARD, grant agreement no. 227579
cern.ch/accnet
Part 1 – LEP3 / TLEP
possible future projects
PSB PS (0.6 km)SPS (6.9 km) LHC (26.7 km)
TLEP (80 km, e+e-, up to 400 GeV c.m.) L(350GeV)≈7x1033cm-2s-1
L(240GeV)≈5x1034cm-2s-1
L(160GeV)≈1.5x1035cm-2s-1
L(91GeV)≈1036cm-2s-1
VHE-LHC (pp, up to 100 TeV c.m.)
also: e± (200 GeV) – p (7 & 50 TeV) collisions
LEP3L(240GeV)≈1034cm-2s-1
L(160GeV)≈5x1034cm-2s-1
L(91GeV)≈2x1035cm-2s-1
LEP3/TLEP luminosity limits
𝐿= 𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏2
4𝜋 𝜎𝑥𝜎 𝑦=( 𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏)(𝑁 𝑏
𝜀𝑥) 14𝜋 1
√𝛽𝑥 𝛽𝑦
1𝜅𝜀
𝑁𝑏
𝜀𝑥=𝜉 𝑥2𝜋𝛾 (1+𝜅𝜎 )
𝑟 𝑒
( 𝑓 𝑟𝑒𝑣𝑛𝑏𝑁 𝑏)=𝑃𝑆𝑅𝜌
8.8575×10−5mGeV−3 𝐸
4
𝑁 𝑏
𝜎 𝑥𝜎𝑧
30𝛾𝑟𝑒2
𝛿𝑎𝑐𝑐𝛼<1
SR radiation power limit
beam-beam limit
>30 min beamstrahlung lifetime (Telnov) → Nb,bx
boosting LEP3/TLEP luminosity
minimizing ke=ey/ex
by~bx(ey/ex)
increases the luminosity independently of previous limits
however by≥sz (hourglass effect)
rf efficiency (Pwall→PSR)compare numbers from LHeC Conceptual Design Report: J L Abelleira Fernandez et al, “A Large Hadron Electron Collider at CERN Report on the Physics and Design Concepts for Machine and Detector,” J. Phys. G: Nucl. Part. Phys. 39 075001 (2012):
conversion efficiency grid to amplifier RF output = 70%transmission losses = 7%feedbacks power margin = 15%→ total efficiency ~55%
50% assumed for LEP3/TLEP at same frequency & gradient
LEP2 LHeC LEP3 TLEP-Z TLEP-H TLEP-tbeam energy Eb [GeV] circumference [km] beam current [mA] #bunches/beam #e−/beam [1012] horizontal emittance [nm] vertical emittance [nm] bending radius [km] partition number Jε momentum comp. αc [10−5] SR power/beam [MW] β∗
x [m] β∗
y [cm] σ∗
x [μm] σ∗
y [μm] hourglass Fhg ΔESR
loss/turn [GeV]
104.526.7442.3480.253.11.118.5111.552703.50.983.41
6026.710028085652.52.61.58.1440.181030160.990.44
12026.77.244.0250.102.61.58.1500.20.1710.320.596.99
45.58011802625200030.80.159.01.09.0500.20.1780.390.710.04
1208024.38040.59.40.059.01.01.0500.20.1430.220.752.1
175805.4129.020 0.19.01.01.0500.20.1630.320.659.3
LEP3/TLEP parameters -1
LEP2 LHeC LEP3 TLEP-Z TLEP-H TLEP-tVRF,tot [GV] dmax,RF [%]ξx/IP ξy/IPfs [kHz] Eacc [MV/m] eff. RF length [m] fRF [MHz] δSR
rms [%] σSR
z,rms [cm] L/IP[1032cm−2s−1] number of IPs Rad.Bhabha b.lifetime [min] ϒBS [10−4] nγ/collision DdBS/collision [MeV] DdBS
rms/collision [MeV]
3.640.770.0250.065 1.67.54853520.221.611.2543600.20.080.10.3
0.50.66N/AN/A0.6511.9427210.120.69N/A1N/A0.050.160.020.07
12.05.70.090.082.19206007000.230.319421890.603144
2.04.00.120.121.29201007000.060.19103352 7440.413.66.2
6.09.40.100.100.44203007000.150.174902 32150.504265
12.04.90.050.050.43206007000.220.25652 54150.516195
LEP3/TLEP parameters -2 LEP2 was not beam-beam limited
LEP data for 94.5 - 101 GeV consistently suggest a beam-beam limit of ~0.115 (R.Assmann, K. C.)
top-up injectionSPS as LEP injector accelerated e± from 3.5 to 20 GeV (later 22 GeV) on a very short cycle: acceleration time = 265 ms or about 62.26 GeV/s Ref. K. Cornelis, W. Herr, R. Schmidt, “Multicycling of the CERN SPS: Supercycle Generation & First Experience with this mode of Operation,” Proc. EPAC 1988
assuming injection from the SPS into the top-up accelerator at the same energy of 20 GeV and final energy of 120 GeV: acceleration time = 1.6 seconds
total cycle time = 10 s looks conservative (→ refilling ~1% of the LEP3 beam, for tbeam~16 min)Ghislain Roy & Paul Collier
transverse impedance & TMCILEP bunch intensity was limited by TMCI: Nb,thr~5x1011 at 22 GeV
LEP3 with 700 MHz: at 120 GeV we gain a factor 5.5 in the threshold, which almost cancels a factor (0.7/0.35)3 ~ 8 arising from the change in wake-field strength due to the different RF frequency
LEP3 Qs~0.2, LEP Qs~0.15: further 25% increase in TMCI threshold?
only ½ of LEP transverse kick factor came from SC RF cavities
LEP3 beta functions at RF cavities might be smaller than in LEP
LEP3 bunch length (2-3 mm) is shorter than at LEP injection (5-9 mm) M. Lamont, SL-Note-98-026 (OP)
simulations by K. Ohmi – later at this meeting
beam-beam with large hourglass effect?
circular Higgs factories become even more popular around the world
LEP3 2011
SuperTristan 2012LEP3 on LI, 2012
LEP3 in Texas, 2012
FNAL site filler, 2012West Coast design, 2012
Chinese Higgs Factory, 2012
UNK Higgs Factory, 2012
Part 2 - SAPPHiRE
“Higgs” strongly couples to ggLHC CMS result LHC ATLAS result
a new type of collider?g
g
Ht, W, …
gg collider Higgs factory
another advantage:no beamstrahlung→ higher energy reachthan e+e- colliders
s-channel production;lower energy;no e+ source
combining photon science & particle physics!
K.-J. Kim, A. SesslerBeam LineSpring/Summer 1996
gg collider
few J pulseenergy with l~350 nm
𝐸𝛾 ,𝑚𝑎𝑥=𝑥1+𝑥 𝐸𝑏𝑒𝑎𝑚
example x ≈ 4.3 (for x>4.83 coherent pair production occurs)
66 GeVECM,max GeV
Ephoton ~3.53 eV , l~351 nm
which beam & photon energy / wavelength?
Source: Fiber Based High Power Laser Systems, Jens Limpert, Thomas Schreiber, and Andreas Tünnermann
power evolution of cw double-cladfiber lasers with diffraction limited beam quality over one decade:factor 400 increase!
laser progress: example fiber lasers
passive optical cavity →relaxedlaserparameters
K. Moenig et al, DESY Zeuthen
self-generated FEL g beams (instead of laser)?
opticalcavity mirrors
wigglerconverting somee- energy into photons (l≈350 nm)
e- (80 GeV)
e- (80 GeV)
Comptonconversionpoint
gg IP
e- bende- bend
example: lu=50 cm, B=5 T, Lu=50 m, 0.1%Pbeam≈25 kW
“intracavity powers at MW levels are perfectly reasonable” – D. Douglas, 23 August 2012
scheme developed with Z. Huang
SAPPHiRE: a Small gg Higgs Factory
SAPPHiRE: Small Accelerator for Photon-Photon Higgs production using Recirculating Electrons
scale ~ European XFEL,about 10k Higgs per year
SAPPHiRE symbol valuetotal electric power P 100 MWbeam energy E 80 GeVbeam polarization Pe 0.80bunch population Nb 1010
repetition rate frep 200 kHzbunch length sz 30 mmcrossing angle qc ≥20 mradnormalized horizontal emittance gex 5 mmnormalized vertical emittance gey 0.5 mmhorizontal IP beta function bx* 5 mmvertical IP beta function by* 0.1 mmhorizontal rms IP spot size sx* 400 nmvertical rms IP spot size sy* 18 nmhorizontal rms CP spot size sx
CP 400 nmvertical rms CP spot size sy
CP 180 nme-e- geometric luminosity Lee 2x1034 cm-2s-1
Valery Telnov’s comments(21 October 2012)
“SUPPHiRE will not work. I considered this approach many years ago, thought about the usage of some existing ring for this purpose, but the problem was clear - unacceptable increase of the emittance”“PLC needs polarized electrons (only in this case one can see the Higgs). At present low emittance polarized electron guns do not exist.”
beam energy [ GeV] DEarc [GeV] DsE [MeV]10 0.0006 0.03820 0.009 0.4330 0.05 1.740 0.15 5.050 0.36 1060 0.75 2070 1.39 3580 1.19 27
total 3.89 57
Energy lossThe energy loss per arc is For r=764 m (LHeC design) the energy loss in the various arcs is summarized in the following table. We lose about 4 GeV in energy, which can be compensated by increasing the voltage of the two linacs from 10 GV to 10.5 GV. We take 11 GV per linac to be conservative.
Energy spread
The additional energy spread from the synchrotron radiation is given by
where R~1 km is the geometric radius, and r the bending radius of the arc. It is also listed in the table. The total rms energy spread induced by synchrotron radiation is only 0.071%.
Emittance growth
The emittance growth is
with Cq=3.8319x10-13 m, and r the bending radius.
For LHeC RLA design with lbend~10 m, and r=764 m, <H>=1.2x10-3 m [Bogacz et al], close to the “useful and realistic” minimum emittance optics of Lee Teng. At 60 GeV the emittance growth of LHeC optics is 13 micron, too high for our purpose, and extrapolation to 80 GeV is unfavourable with 6th power of energy. From Teng we also have scaling law . This suggests that by reducing the cell length and dipole length by a factor of 4 we can bring the horiz. norm. emittance growth at 80 GeV down to 1 micron.
reference
“Sawtooth” orbit
The largest energy loss due to synchrotron radiation for beams in a common arc occurs at 70 GeV. It amounts to 1.39 GeV, or 2%. With a dispersion of 0.1 m (see [Bogacz et al]) the orbit change would be 2 mm. The two beams would certainly fit into a common beam pipe.
Flat electron source
We would like to operate with flat beams, with an emittance ratio of 10. Such flat beam can be produced with a flat-beam electron gun using the flat-beam transformer concept of Ref. [Derbenev et al]. Starting with a normalized uncorrelated emittance of 4-5 mm at a bunch charge of 0.5 nC, the injector test facility at the Fermilab A0 line achieved emittances of 40 mm horizontally and 0.4 mm vertically, with an emittance ratio of 100. For the gamma-gamma collider we only need an emittance ratio of 10, but a three times larger charge (1.6 nC) and a smaller initial emittance of ~1.5 mm. These parameters are within the present state of the art (e.g. the LCLS photoinjector routinely achieves 1.2 mm emittance at 1 nC charge). However, we need a polarized beam…
can we get ~ 1-nC polarized e- bunches with ~1 mm emittance?
ongoing R&D efforts:
DC gun (MIT-Bates, Cornell, SACLA,…)
polarized SRF gun (FZD, BNL,…)
Schematic sketches of the layout for the LHeC ERL (left) and for a gamma-gamma Higgs factory based on the LHeC (right)
LHeC → SAPPHiRE
would it fit on SLAC site?
schematic of HERA-gg
3.6 GeVLinac(1.3 GHz)
3.6 GeVlinac
2x1.5 GeVlinac
IP
laser or auto-driven FEL
2x8+1 arcs
0.5 GeV injector
real-estatelinacGradient~ 10 MV/m
totalSC RF =10.2 GV
20-MV deflectingcavity (1.3 GHz)
5.6 GeV15.826.036.246.055.363.871.171.163.855.246.036.226.015.85.6
75.8 GeV
arc magnets -17 passes!
20-MV deflectingcavity
beam 1
beam 2
r=564 m for arc dipoles (probably pessimistic; value assumed in the following)
F. Zimmermann, R. Assmann, E. Elsen,DESY Bschleuniger-Ideenmarkt, 18 Sept. 2012
γγ Collider at J-Lab
𝑯𝟎
By Edward NissenTown Hall meeting Dec 19 2011
similar ideas elsewhere
Background
γ
γ H
ћ
𝑥=12.3𝐸𝑒(𝑇𝑒𝑉 )λ𝛾(𝜇𝑚)
arXiv:hep-ex/9802003v2
Edward Nissen
Possible Configurations at JLAB
85 GeV Electron energyγ c.o.m. 141 GeV
103 GeV Electron energyγ c.o.m. 170 GeV
Edward Nissen
LEP3, TLEP, and SAPPHiREare moving forward
thank you for listening!
