1. NLC - The Next Linear Collider Project NLC IR Layout and Background Estimates Jeff Gronberg/LLNL For the Beam Delivery Group LCWS - October 25, 2000

2. NLC - The Next Linear Collider Project New IR model Beam Delivery Backgrounds: Tom Markiewicz (SLAC) Pairs and Neutron Backgrounds Takashi Maruyama (SLAC) Jeff Gronberg (LLNL) Synchrotron Radiation Stan Hertzbach (U. Mass) Muons, Collimator Efficiency Lew Keller (SLAC) Changes since Berkeley: –Raimondi Final Focus –L* = 4.3 m –Large Detector –500 GeV c.o.m. This talk has: –NEW calculations for pairs & radiative bhabhas charged hits, photons, & neutrons –NEW muon background calculations –OLD dump neutron estimate

3. NLC - The Next Linear Collider Project LCD-L2 (3T) with 4.3m L* Optics QD0 SD0 M1 Calorimeter Pair LumMon M2 Beampipe Low Z shield 30 mrad Cal acceptance Support Tube

4. NLC - The Next Linear Collider Project Pair hits at z = 4 m  4cm  2cm

5. NLC - The Next Linear Collider Project Hit Densities vs. Radius LCD-L(4T) & S(6T) at 1 TeV March 2000 LCD-L(3T) at 1 and 0.5 TeV October 2000

6. NLC - The Next Linear Collider Project Neutron Production from Pairs with Be absorber 10 cm absorber 50 cm absorber

7. NLC - The Next Linear Collider Project VXD Neutron Dose Rate OLD PAIR & RB Estimate OLD but still VALID DUMP & Dumpline Estimate NEW PAIR & RB Estimate

8. NLC - The Next Linear Collider Project Neutron Hit Density vs. Extraction Line Aperture Particles showering close to the IR are bad for neutrons. Increasing extraction line aperture transports them farther away.

9. NLC - The Next Linear Collider Project NEW Hi/Lo NLC Layout WITHOUT Big Bend

10. NLC - The Next Linear Collider Project Muon Spoiler Locations

11. NLC - The Next Linear Collider Project 250 GeV/beam Muon Endcap Background Engineer for 10 -3 Halo Bunch Train =10 12 Calculated Halo is 10 -6 Efficiency of Collimator System is 10 5

12. NLC - The Next Linear Collider Project 500 GeV/beam Muon Endcap Background Engineer for 10 -3 Halo Bunch Train =10 12 Calculated Halo is 10 -6 Efficiency of Collimator System is 10 5

13. NLC - The Next Linear Collider Project 250 GeV/beam Endcap CAL Background Engineer for 10 -3 Halo Bunch Train =10 12 Calculated Halo is 10 -6 Efficiency of Collimator System is 10 5

14. NLC - The Next Linear Collider Project Synchrotron Radiation Calculations Halo –QD0 and QF1 –Limiting Apertures Beam Pipe Radius Extraction Line Shielding Core –Soft Bend 30-150m UNDER Review Less than Optimal Beam at Turn On –How conservative do you want to be? Emittance Energy Tails

15. NLC - The Next Linear Collider Project Halo SR at the Beam Pipe Assumes 1E-3 halo E  ~ 3-4 MeV Sextupoles not yet included Effective vs. Ideal accounts for 1% beam energy spread and planar collimation Flare Min. radius

16. NLC - The Next Linear Collider Project HALO Synchrotron Radiation Fans with Nominal 240  rad x 1000  rad Collimation

17. NLC - The Next Linear Collider Project SR from the Bends in Two FF Designs Masks outside of 12  beam stay-clear at 45m & 100m from IP absorb soft bend SR Soft bend ends 18m from IP: working to fix this without adding too much length to FF ZDRLCWS

18. NLC - The Next Linear Collider Project Ultimate Limit on Beam Pipe Radius Energy Tails If the vertex detector radius is very small, synchrotron radiation from the core Gaussian beam sets the limit. Vertex detector hit density ~hit density on beam pipe. SR Hit Density (hits/mm 2 ) on Inner Wall of Beam Pipe for 3 collimation depths and as beam energy varies

19. NLC - The Next Linear Collider Project Ultimate Limit on Beam Pipe Radius Larger Emittance Allow for larger than nominal emittance Gaussian beam. –Startup issues. –Factor of 2 in beam size is factor of 4 in emittance. –Running below nominal energy (500 GeV Ecm) will mean reduced luminosity and/or larger emitttance. SR Hit Density (hits/mm 2 ) on Inner Wall of Beam Pipe

20. NLC - The Next Linear Collider Project Conclusions Charged Particles; –Beryllium ring is gone, VXD hits still limited by direct particles Neutrons –Improvement from L*=4.3m, study low-Z shielding and apertures –Redo dump neutrons for new apertures Synchrotron radiation –New FF, new situation Final doublet ok, masking for soft bend must rethink Muons –With short final focus big bend makes no difference –Spoilers can reduce background to acceptable level