CLIC Interaction Region when beams meet detectors Barbara Dalena (CERN BE/ABP-CC3 ) LAL 25th January 2011

Outline Introduction Solenoid effects on beam dynamics Interaction Region (IR) Solenoid Solenoid effects on beam dynamics Optical distortions Compensation Incoherent Synchrotron Radiation Impact of IR magnet designs on luminosity loss Beam-related backgrounds and luminosity measurement signal 25/1/2011 B. Dalena, LAL seminar

CLIC layout @ 3 TeV Drive beam Main beam Drive Beam Generation Complex Main Beam Generation Complex 25/1/2011 B. Dalena, LAL seminar

Detector Solenoid

Solenoids Instrumented Return Yoke Superconductive coils + instrumented return yoke Engineering based on CMS experience Coil 6 m B [T] Rin [m] ILD 4 3.395 SiD 5 2.684 25/1/2011 B. Dalena, LAL seminar

Why and which magnetic field ? General considerations  PT fit : Measurement errors in curvature and direction MS : Multiple scattering errors 25/1/2011 B. Dalena, LAL seminar

Errors on track momentum and direction Measurement errors L’ : trajectory on the plane orthogonal to B L : total trajectory  : resolution in the plane orthogonal to B z : resolution in the z direction N + 1 : number of measurement points Multiple scattering Pagina 39-40 e in poi della tesi di elena botta where X0 : radiation length of the scattering medium LC-measurements require 25/1/2011 B. Dalena, LAL seminar

B-field and beam-beam background Higher solenoid magnetic field confines more the beam-beam secondary particles  reduce background in the detector Takashi Maruyama 25/1/2011 B. Dalena, LAL seminar

Effects on the beams

Solenoid and beam crossing angle Schematic view of the two beams colliding with a crossing angle in the detector solenoid. Vertical orbit of e+ e- beams colliding with a crossing angle in the detector solenoid for different magnetic field. 25/1/2011 B. Dalena, LAL seminar

Solenoid beam dynamics Orbit deviation : the beam is bent as it traverses the magnetic field Weak focusing : in the two transverse planes Coupling between x-y plane : the particle position in one plane depends on the position in the other plane Dispersion : particles at lower energies experience a larger deflection than those at higher energies The beam emits Incoherent Synchrotron Radiation (ISR) as it is deflected Bxcosc and Bzsinc act on the beam with opposite sign Br  r x’’  Br  y y’’  Br  x x’’  e/cp y’’  e/cp Ps  1/(m0c2)4  E4 / R2 25/1/2011 B. Dalena, LAL seminar

Detector Solenoid magnetic fields x s θc/2 z x, z solenoid axes s beam line longitudinal axis Different detector designs generate different field along the beamline 25/1/2011 B. Dalena, LAL seminar

Main field component acting on the beam Mult QD0 L* IP BX component of solenoid fields in the beamline reference system CLIC_SiD H. Gerwig (CERN) CLIC_ILD D. Swoboda (CERN) 4th concept J. Hauptman (Iowa State University) 25/1/2011 B. Dalena, LAL seminar

Orbit deviations Mult QD0 IP Vertical orbit deviations due to the detector solenoid field and its overlap with QD0 (and the other FF magnets) 25/1/2011 B. Dalena, LAL seminar

Vertical offset correction QD0 Mult Vertical offset at IP compensated by QD0 offset 25/1/2011 B. Dalena, LAL seminar

Distortions in the transverse plane 25/1/2011 B. Dalena, LAL seminar

IR coupling compensation When detector solenoid overlaps QD0, coupling between y & x’ and y & E causes large (30 – 190 times) increase of IP size (green=detector solenoid OFF, red=ON) without compensation sy/ sy(0)=32 Even though traditional use of skew quads could reduce the effect, the local compensation of the fringe field (with a little skew tuning) is the most efficient way to ensure correction over wide range of beam energies antisolenoid QD0 SD0 with compensation by antisolenoid sy/ sy(0)<1.01 25/1/2011 B. Dalena, LAL seminar A.Seryi, ILC Accelerator School 2010

Compensation of the optical distortions Bucking coils that cancel the main solenoid field in the magnets region reduce the beam distortions at the IP QD0 shielding from the main solenoid field R  25 cm LIP  3.5 m CLIC_ILD QD0 25/1/2011 B. Dalena, LAL seminar

Anti-solenoid design H. Gerwig CERN PH-CMX Anti-solenoid integration: - 4 bucking coils of same length and equally spaced CLIC_SiD R 50 cm LIP  3.8 m CLIC CLIC CLIC CLIC CLIC CLIC CLIC CLIC QD0 25/1/2011 B. Dalena, LAL seminar

Anti-solenoids impact on the beams 25/1/2011 B. Dalena, LAL seminar

|corr(y,E)|/beam sizes |corr(y,x’)|/beam sizes Optical compensation |corr(y,E)|/beam sizes ILD SiD |corr(y,x’)|/beam sizes IP offset m Main Solenoid 27.09 35.99 19.42 23.01 -4.421 -6.417 Solenoid + Anti-solenoid 0.84 1.60 1.02 1.62 +0.069 -0.736 more than 90% of the distortions are corrected by the anti-solenoid how much of residual distortions can be cancelled with other FFS magnets ? ex: sextupoles knobs (constructed by E. Marin BE/ABP-CC3 ) sextupole offsets O(10) m knobs knobs 25/1/2011 B. Dalena, LAL seminar

Anti-solenoid optimization To reach the QD0 gradient, external field should be low (due to permendur material) optimize anti-solenoid bucking coils shape and/or adding ferromagnetic material shift QD0 far from IP if first solution not feasible insure it still reduces up to 90% the optical distortions of the beam at the IP Work in progress A. Bartalesi CERN TE-MSC 25/1/2011 B. Dalena, LAL seminar

Incoherent Synchrotron radiation

Incoherent Synchrotron Radiation sources in the BDS Bending magnets in the FFS about 10% luminosity loss in CLIC 3 TeV CM vg = c ve < c A.Seryi, ILC Accelerator School 2010 Strong focusing in the final doublet (Oide effect) about 10% of luminosity loss in CLIC 3 TeV CM Final quad R L L* IP 25/1/2011 B. Dalena, LAL seminar

Effect on the beam sizes Beam size increase at the IP due to Incoherent synchrotron radiation FFS Bend Final Doublet Solenoid 25/1/2011 B. Dalena, LAL seminar

Luminosity Loss due to incoherent synchrotron radiation Field Map Bz [T] Lumi loss [%] CLIC(ILC)_SiD 5 ~(3)14.0 CLIC_SiD + Antisolenoid ~10.0 CLIC(ILC)_ILD 4 ~(4)10.0 CLIC_ILD + Antisolenoid 4th concept at 3TeV 3.5 ~20.0 ILC_ILD at 3 TeV + AntiDiD ~25.0 Luminosity calculation by GUINEA-PIG CLIC half horizontal crossing angle 10 mrad CLIC-BDS budget: 20% luminosity loss 25/1/2011 B. Dalena, LAL seminar

DiD - AntiDiD Bx DiD θc/2 AntiDiD θc/2 Coil wound on detector solenoid giving transverse field (Bx) It can zero y and y’ at IP But the field acting on the outgoing beam is bigger than solenoid detector alone  pairs diffuse in the detector AntiDiD Reversing DiD’s polarity and optimizing the strength, more than 50% of the pairs are redirected to the extraction apertures θc/2 θc/2 25/1/2011 B. Dalena, LAL seminar

Position of emitted photons Mean energy of emitted photons ~ 20 MeV, peak at very low energy (< 1 MeV) max photon energy ( < 200 MeV) 25/1/2011 B. Dalena, LAL seminar

Photon fans at the IP Collimation depths : x = 15x , y = 55y Maximum photon cone for an envelope covering 15x and 55y 25/1/2011 B. Dalena, LAL seminar

Luminosity measurements

FFS luminosity optimization Static imperfections luminosity optimization only: 55% of the seeds reach 100% of nominal luminosity. after 2 iterations of H and V knobs: 90% of the seed reach 90% of nominal luminosity (identical machines) luminosity optimization needs O( 10000 ) luminosity measurements Knobs tuning 20 points  8 knobs  2 iter = 320 luminosity measurements 25/1/2011 B. Dalena, LAL seminar

Luminosity measurement signal radiative bhabha : high counting rate but not really visible in the spent beam spectrum low angle bhabha 7-70 minutes for 1% luminosity measurement according to the  cut long term luminosity stability due to dynamic imperfections 10-30 minutes we need a luminosity measurement signal  1 min 25/1/2011 B. Dalena, LAL seminar

Knobs vs luminosity and background (H) 25/1/2011 B. Dalena, LAL seminar

Knobs vs luminosity and background (V) Incoherent pairs & hadronic events  luminosity 25/1/2011 B. Dalena, LAL seminar

Hadronic events multiplicity No Pt cut applied Nhadron per bx are ~3.21 Which particles are visible in the detector ? 25/1/2011 B. Dalena, LAL seminar

Multiplicity per train (example: +/-) 3 train : Mult rms ~ 7% (@ 1 <  < 1.57 rad) how much of this multiplicity is visible ? 25/1/2011 B. Dalena, LAL seminar

Summary & Conclusions Detector solenoid design and related IR magnets can have a strong impact on the CLIC achievable luminosity Anti-solenoid can reduce up to > 90% the optical distortions due to the interaction region solenoid and QD0 overlap First look at the hadrons as potential fast luminosity measurement signal 25/1/2011 B. Dalena, LAL seminar

References Acknowledgement R.L. Gluckstern Nucl. Instrument and Methods 24 (1963) 381-389 R. Tomás et al., « Summary of the BDS and MDI CLIC08 Working group » CLIC-Note-776 B. Dalena et al., « Solenoid and Synchrotron Radiation Effects in CLIC » PAC’09-TH6PFP074 and CLIC-Note-786 D. Swodoba, B. Dalena and R. Tomás « CLIC spectrometer magnet interference computation of transversal B-field on primary beam » CLIC-Note-815 B. Dalena et al., « Impact of the Experimental Solenoid on the CLIC luminosity » IPAC’10-WEPE029 and CLIC-Note-831 J. Resta Lopez et al., « Optimization of the CLIC Baseline Collimation System » IPAC’10-WEPE046 B. Dalena and D. Schulte << Beam-Beam background in CLIC in presence of imperfections >> IPAC’10-WEPE025 Acknowledgement Many thanks to D. Schulte, K. Elsener and André Sailer for useful discussions. 25/1/2011 B. Dalena, LAL seminar

spares

Energy distribution 25/1/2011 B. Dalena, LAL seminar

Hadronic events multiplicity Mult (rms) (0<<1.57 rad) Mult (rms) (0<<0.5 rad) Mult (rms) (0.5<<1 rad) Mult (rms) (1<<1.57 rad) e+/- 0.0967(0.4405) 0.06903 (0.3689) 0.01518(0.1612) 0.01249(0.1443) +/- 0.007877 (0.09525) 0.006306 (0.08465) 0.0008891 (0.03046) 0.0006819 (0.02645)  7.429 (8.648) 5.271(6.64) 1.193(1.859) 0.9651(1.562) +/- 6.584(6.858) 4.919(5.409) 0.946(1.441) 0.7191(1.173) K+/- 0.7285(1.247) 0.5797(1.076) 0.08778(0.3259) 0.06103(0.2656) KoL 0.3525(0.7278) 0.2794(0.634) 0.04285(0.2155) 0.02928(0.176) p 0.42(0.907) 0.3462(0.8011) 0.04478(0.2276) 0.02898(0.1795) n 0.3975(0.8763) 0.3267(0.7719) 0.04297(0.2225) 0.02782(0.1754) incoh. pairs* 297504 (1292) 293998 (1289) 3342.67 (64.29) 162.94 (14.43) * incoherent pairs are per bx, hadronic events are per  collision (Nhadron are ~3.21 per bx) 25/1/2011 B. Dalena, LAL seminar

CLIC crossing angle 10 mrad half crossing angle 25/1/2011 B. Dalena, LAL seminar

Incoherent pairs diffusion in ILC Solenoid only DID anti-DID A. Seryi et al., SLAC-PUB-11662 25/1/2011 B. Dalena, LAL seminar

Incoherent pairs diffusion in CLIC deposited energy ~ 27 TeV per bx A. Sailer CERN PH-LCD 25/1/2011 B. Dalena, LAL seminar

Backscattered particles A. Sailer CERN PH-LCD 25/1/2011 B. Dalena, LAL seminar