Technical Systems in the PostCollision Line Edda Gschwendtner

Technical Systems in the Post-Collision Line Edda Gschwendtner, CERN for the Post-Collision Working Group Rob Appleby (CERN & Cockcroft Institute), Armen Apyan (CERN), Konrad Elsener (CERN), Arnaud Ferrari (Uppsala University), Thibaut Lefevre (CERN), Cesare Maglioni (CERN), Alessio Mereghetti (CERN), Michele Modena (CERN), Mike Salt (Cockcroft Institute), Jan Uythoven (CERN), Ray Veness (CERN), Alexey Vorozhtsov (CERN)

2 Outline • • • Design Considerations 500 Ge. V/18. 6 mrad Option Background Calculations to the IP Absorbers and Intermediate Dump Magnet System Vacuum System Main Beam Dump Luminosity Monitoring Summary E. Gschwendtner, CERN

3 Design Considerations • • • Transport particles of all energies and intensities from IP to dump Diagnostics (luminosity monitoring) Control beam losses in the magnets Minimize background in the experiments Stay clear of the incoming beam Consequences Large acceptance Collimation system Main dump protection system Beam diagnostic system E. Gschwendtner, CERN

4 Some Numbers 50 Hz repetition rate 3. 7 E 9 e/bunch 14 MW beam power • • e+e- collision creates disrupted beam – Huge energy spread, large x, y div in outgoing beam total power of ~10 MW High power divergent beamstrahlung photons – 2. 2 photons/incoming e+e 2. 5 E 12 photons/bunch train total power of ~4 MW • Coherent e+e- pairs – 5 E 8 e+e- pairs/bunch. X 170 k. W opposite charge • 156 ns bunch train length 312 bunches/pulse Incoherent e+e- pairs – 4. 4 E 5 e+e- pairs/bunch. X 78 W E. Gschwendtner, CERN

5 Baseline Design intermediate dump carbon based masks 1. 5 m side view ILC style water dump C-shape magnets 27. 5 m window-frame magnets 67 m 6 m 4 m 273 m 1. Separation of disrupted beam, beamstrahlung photons and particles with opposite sign from coherent pairs and particles from e+e- pairs with the wrong-sign charge particles Intermediate dumps and collimator systems 2. Back-bending region to direct the beam onto the final dump Allowing non-colliding beam to grow to acceptable size E. Gschwendtner, CERN

6 Civil Engineering Layout Yesterday: Length between IP and main beam dump is 273 m Today: 315 m E. Gschwendtner, CERN

7 500 Ge. V c. m. /18. 6 mrad Option 3 cm rms 250 Ge. V Beam at 150 m from IP at 1. 5 Te. V beamstrahlung Disrupted beam 1. 5 Te. V 80 cm y’max= ± 1 mrad Photons: 19 cm horizontal shift, but reduced in size Proof of principle Impact of 500 Ge. V c. m. scenario on post-IP design is minimal E. Gschwendtner, CERN Right-sign coherent pairs x’max = ± 0. 6 mrad x’maxy’=max ± 1. 6 mrad = ± 0. 3 mrad y (cm) 19 cm shift

8 Background Calculations to IP E. Gschwendtner, CERN

9 Background from Intermediate Dump to IP IP From first absorber: 0. 73 ± 0. 05 photons/cm 2/bunch. X From intermediate dump: 7. 7 ± 2. 6 photons/cm 2/bunch. X (without absorbers: 530 ± 20 photons/cm 2/bunch. X) Intermediate dump contributes significantly to IP background But 98% attenuation thanks to magnetic chicane M. Salt, Cockcroft Institute E. Gschwendtner, CERN

10 Background Calculations from Main Dump to IP • Entire Post-collision line geometry implemented • Using Geant 4 on the GRID Ongoing: M. Salt, Cockcroft Institute – Neutron and photon background from main beam dump window-frame magnets intermediate dump C-shaped magnets masks Preliminary results show that background particles at ‘outer edge’ of the LCD is low and detectors should absorb large fraction of particles. Even if additional absorbers are needed, space is available in the detector forward region.

11 Magnet Protection Absorbers and Intermediate Dump E. Gschwendtner, CERN

12 Absorber Baseline Design 170 k. W Aperture dimensions tuned such that losses in magnets < 100 W/m Opposite charge particles 1. 9 k. W 0. 7 k. W 131 k. W 3. 1 k. W 0 k. W 6. 9 k. W 0. 9 k. W 4 k. W Same charge particles Magnet protection: Carbon absorbers: a) 1. 00 m x 0. 5 m aperture: Y=13. 2 cm b) 1. 54 m x 0. 77 m x 0. 9 m aperture: Y=25. 6 cm c) 1. 89 m x 0. 95 m x 0. 9 m aperture: Y= 57 cm d) 2. 24 m x 1. 12 m x 0. 9 m aperture: Y= 92. 6 cm Intermediate dump (CNGS style): carbon based absorber, water cooled aluminum plates, iron jacket 3. 15 m x 1. 7 m x 6 m aperture: X=18 cm, Y=86 cm Non-trivial, but solutions for absorbers exist (see dumps in neutrino experiments: 4 MW) E. Gschwendtner, CERN

13 Magnets E. Gschwendtner, CERN

Post-Collision Line Magnets Designed considerations: • average current density in copper conductor < 5 A/mm 2. • magnetic flux density in magnet core is < 1. 5 T. • temperature rise of cooling water < 20° K. Quantity Magnetic length Full magnet aperture horiz. / vert. [m] Full magnet dimensions Horiz. / vert. [m] Strength Power consumption Mag 1 a 1 b 2 x 2 2 m 0. 222 / 0. 57 0. 998 / 1. 480 0. 8 T 65 k. W Mag 2 1 x 2 4 m 0. 296 / 0. 839 1. 118 / 1. 850 0. 8 T 162. 2 k. W Mag 3 1 x 2 4 m 0. 370 / 1. 157 1. 154 / 2. 260 0. 8 T 211 k. W Mag 4 1 x 2 4 m 0. 444 / 1. 531 1. 344 / 2. 840 0. 8 T 271 k. W Mag. C-type 1 x 2 4 m 0. 45 / 0. 75 1. 918 / 1. 850 0. 8 T 254 k. W Dipole names In total 18 magnets of 5 different types Total consumption is 3. 3 MW Total cost: 12. 2 MCHF M. Modena, A. Vorozhtsov, TE-MSC

Magnets C-type Mag 1 a Incoming beam 5. 1 cm Mag 1 a Mag 1 b 27. 5 m 30. 5 m 20. 1 cm 11. 1 cm Mag 2 38 m 40. 8 cm 34. 3 cm 54. 1 cm spent beam Mag 3 Mag 4 46 m 54 m Ctype 75 m

Magnets Mag 1 a 1 b 4. 6 A/mm 2 280 k. CHF 65 k. W 10 A/mm 2 198 k. CHF 143 k. W 5. 1 cm distance to incoming beam 19. 5 cm distance to incoming beam Non-trivial, but solutions exist M. Modena, A. Vorozhtsov, TE-MSC

17 Vacuum System E. Gschwendtner, CERN

18 Vacuum System elliptical vacuum tube • Less demanding pressure requirement in the medium vacuum range [required pressure TBC], – allowing for a conventional un-baked system design. • Requires a high pumping speed due to the large surface area and beaminduced outgassing. – A combination of sputter-ion, turbo-molecular and mechanical pumps will be used. • stainless steel vacuum chambers in stepped or conical forms inside the magnetic and absorber elements. • Absorbers are outside the vacuum chambers – windows upstream of the intermediate dump absorbers – exit window separating the collider vacuum system from the main dump body. Cost estimate: 2. 2 MCHF Non-trivial, but solutions exist E. Gschwendtner, CERN R. Veness, TE-VSC

19 Main Beam Dump E. Gschwendtner, CERN

20 Baseline Main Dump Design • 1966: SLAC water based beam dump: 2. 2 MW • 2008: ILC 18 MW water dump – – Cylindrical vessel 30. 0 cm Volume: 18 m 3, Length: 10 m diameter window (Ti) Diameter of 1. 5 m 1. 0 mm thick Water pressure at 10 bar (boils at 180 C) 15. 0 mm thick Ti vessel Diameter 1. 5 m Dump axis Length 10. 0 m – Ti-window, 1 mm thick, 30 cm diameter CLIC ILC Beam energy 1500 Ge. V 250 Ge. V # particles per bunch 3. 7 x 109 2 x 1010 # bunches per train 312 2820 Duration of bunch train 156 ns 950 ms Uncollided beam size at dump sx, sy 1. 56 mm, 2. 73 mm 2. 42 mm, 0. 27 mm # bunch trains per second 50 5 Beam power 14 MW 18 MW E. Gschwendtner, CERN

21 Main Beam Dump • Uncollided beam: sx = 1. 56 mm, sy =2. 73 mm 4. 26 mm 2 • Collided beam: Collided 1. 5 Te. V Beam at 150 m from IP beamstrahlung Disrupted beam Right-sign coherent pairs 30 mm rms A. Ferrari et al E. Gschwendtner, CERN Photons Disrupted Beam Coh. Pairs A. Apyan, EN-MEF

22 Particle Distribution at Entrance Window Coherent pairs disrupted e+/e 10 -3 0 mm Photons 10 -4 10 -3 0 mm 750 mm -750 mm 22 Window Dump A. Mereghetti, EN-STI E. Gschwendtner, CERN

23 Energy Deposition in Main Dump uncollided beam max ≈ 270 J/cm 3 collided beam (x 10) max ≈ 10 J/cm 3 uncollided beam [J cm-3 per bunch train] A. Mereghetti, EN-STI E. Gschwendtner, CERN

Main Dump Issues • Maximum energy deposition per bunch train: 270 J/cm 3 ILC: 240 J/cm 3 for a 6 cm beam sweep • Remove heat deposited in the dump – Minimum water flow of 25 -30 litre/s with v=1. 5 m/s • Almost instantaneous heat deposition generate a dynamic pressure wave inside the bath! – Cause overstress on dump wall and window (to be added to 10 bar hydrostatic pressure). guarantee dump structural integrity: dimensioning water tank, window, etc. . • Radiolytical/radiological effects – Hydrogen/oxygen recombiners, handling of 7 Be, 3 H Calculations ongoing: EN-STI

25 Energy Deposition in Beam Window Total deposited Power: ~6. 2 W Ti-window, 1 mm thick, 30 cm diameter R=15 cm uncollided beam max ≈ 5. 7 J/cm 3 max ≈ 0. 13 J/cm 3 C. Maglioni, EN-STI uncollided beam A. Mereghetti, EN-STI E. Gschwendtner, CERN

Main Dump Window Considerations • Maximum energy deposition per bunch train: 5. 7 J/cm 3 ILC: max total power of ~25 W with 21 J/cm 3 • Beam dump window needs stiffener, double/triple parallel window system, symmetric cooling, etc… to withstand – Hydrostatic pressure of 10 bar – Dynamic pressure wave – Window deformation and stresses due to heat depositions Calculations ongoing for Temperature behavior, and vessel performance: EN-STI

27 Luminosity Monitoring E. Gschwendtner, CERN

28 Luminosity Monitoring e+e- pair production Beamstrahlung through converter Produce charged particles Optical Transition Radiation in thin screen Observation with CCD or photomultiplier m+m- pair production V. Ziemann – Eurotev-2008 -016 Converter in main dump muons install detector behind dump – With a Cherenkov detector: 2 E 5 Cherenkov photons/bunch Converter (1 mm thick C) Small magnetic field (10 -3 Tm) OTR screen (30 mm diameter) E. Gschwendtner, CERN

29 First Results Muon distribution with E> 212 Me. V behind the beam dump and shielding cm cm E. Gschwendtner, CERN A. Apyan, EN-MEF

30 First Results Muon distribution 10 m downstream the beam dump Muons with E>5 Ge. V from: Photons 59% Spent Beam 39% Coh. Pairs 2% Muons with E>50 Ge. V from: Photons 84% Spent Beam 16% Coh. Pairs 0% A. Apyan, EN-MEF E. Gschwendtner, CERN

31 Luminosity Monitoring First results, but still ongoing: EN-MEF Include Cherenkov counters in simulations 50 Ge. V threshold ? ? ? Urgently needed: produce non-perfect collisions and track particles through post collision line to see variations in luminosity detectors New fellow request E. Gschwendtner, CERN

Summary for the Post Collision Line 32 • Magnets: preliminary design ✔ cost estimate ✔. • Vacuum: preliminary design ✔ cost estimate ✔. • Intermediate dumps and masks: concept ok ✔ , cost estimate needed EN-STI: only until end 2010 • Main beam dump: first calculations ongoing, cost estimate needed • Luminosity monitoring: Project associate until end 2011 first promising calculations results, non perfect beam urgently needed • Background calculations to IP: New fellow request nearly done ✔ • 500 Ge. V/18. 6 mrad proof of principle: done ✔ • Civil engineering design change to 315 m: proposal: leave results from 273 m decision E. Gschwendtner, CERN

33 • Additional Slides E. Gschwendtner, CERN

34 Introduction Parameter CLIC Max. Center of Mass energy [Ge. V] 3000 Luminosity L 99% [cm-2 sec-1] 2 1034 Bunch frequency [Hz] 50 Bunch spacing [ns] 0. 5 # Particles per bunch # Bunches per pulse Bunch train length [ms] 3. 7 109 312 0. 156 Beam power per beam [MW] 14 Bunch length [mm] 44 Crossing angle [mrad] 20 Core beam size at IP horiz. sx* [nm] 45 Core beam size at IP vertic. sy* [nm] 0. 9 E. Gschwendtner, CERN

35 Upstream face and window [J cm-3 per bunch train] Dr=2. 5 mm; Df=6. 0 deg; Dz=15. 0 mm; [J cm-3 per bunch train] Dr=0. 5 mm; Df=2. 0 deg; Dz=1. 0 mm; E. Gschwendtner, CERN 35

36 Summary of Energy Deposition in Main Dump max [J cm-3 per bunch train] un-collided H 2 O 271 9. 7 Ti window 5. 7 0. 13 Ti vessel (side) 0. 001341 0. 00292 Ti vessel (upstr. face) 0. 000037 0. 001993 Ti vessel (dwnstr. Face) 0. 254852 0. 044544 E. Gschwendtner, CERN tot [W] un-collided 13. 8 M 6. 40 15. 5 k 7. 3 1. 1 k collided 13. 1 M 4. 76 17. 0 k 45. 0 905. 0