1. NLC - The Next Linear Collider Project Backgrounds Update Tom Markiewicz SLAC LCWS Cornell 15 July 2003

2. Tom Markiewicz NLC - The Next Linear Collider Project Outline Pair Background Energy Conservation –What is getting hit? Backgrounds at Machine Startup –John Jaros asks: What if the machine is 1000x worse than you expect? –A first look…. Muon Background Update –Study by TRC Collimation Task Force sets apertures and calculates source terms –Lew Keller makes & transports muons to the detector wit & without tunnel-filling toroids

3. Tom Markiewicz NLC - The Next Linear Collider Project Pair Refresher Course At 500 Gev w/ NLC beam parameters: 49.2K e- per bunch @ =4.05 GeV 200 TeV Total 0.37mWatts per side

4. Tom Markiewicz NLC - The Next Linear Collider Project Pairs Lost on Lum and QDF1

5. Tom Markiewicz NLC - The Next Linear Collider Project Pair Energy Flow Remaining 81.7% of pairs convert into photons and are absorbed by masks & calorimeters

6. Tom Markiewicz NLC - The Next Linear Collider Project Collimation System Designed to Make Detector Free of Machine Backgrounds E=250 GeV N=1.4E12 0.1% Halo distributed as 1/X and 1/Y for 6<A x <16  x and 24<A y <73  y with  p/p=0.01 gaussian distributed

7. Tom Markiewicz NLC - The Next Linear Collider Project SR at IP due to Halo X (cm) Y Log10(E) (GeV) Quad Bend .3 Ne- =4.8 MeVQuad Bend

8. Tom Markiewicz NLC - The Next Linear Collider Project X-Y at Spoiler #3  30  m x  25  m 6  x <A x <16  x 24  y <A y <73  y  60  m x  50  m 12  x <A x <32  x 48  y <A y <146  y

9. Tom Markiewicz NLC - The Next Linear Collider Project Loss Distribution in “Worst Case” Scenario E=250 GeV N=1.4E12 0.1% Halo distributed as 1/X and 1/Y for 2*6<A x <2*16  x and 2*24<A y <2*73  y with  p/p=0.01 gaussian distributed AND SP/AB/DP x2-x3

10. Tom Markiewicz NLC - The Next Linear Collider Project Worst Case Ray Distribution at Spoiler#1

11. Tom Markiewicz NLC - The Next Linear Collider Project SR at IP in “1000x worse case” SR distribution ~2x wider in y at IP with direct hits unless BP >1.25cm

12. Tom Markiewicz NLC - The Next Linear Collider Project NLC Beam Delivery thru 1999 Protect via distance and “Big Bend” Currently 3x shorter & No Bend

13. Tom Markiewicz NLC - The Next Linear Collider Project Layout of Spoilers, Absorbers & Protection Collimators Betatron Betatron Cleanup Energy FF

14. Tom Markiewicz NLC - The Next Linear Collider Project Calculated Beam Loss: Input to MuCarlo

15. Tom Markiewicz NLC - The Next Linear Collider Project 9 & 18m Toroid Spoiler Walls 4.5m 0.6m 2cm BB 170 Tons/m Design Constraints: Minimize gap & minimize stray field in beampipe

16. Tom Markiewicz NLC - The Next Linear Collider Project First 100 Muons from PC1 of HEIR beamline that reach z=0 IR1 line has 9m & 18m magnetized walls NO 18m wall in IR2 lineIR2 line has 18m wall Somewhat arbitrary Goal: 10 muons / detector / train (from both e-,e+ systems)

17. Tom Markiewicz NLC - The Next Linear Collider Project Muon Yield For 250 GeV p  >1 GeV/c  /e = 5 x 10 -4 Yield scales with beam energy

18. Tom Markiewicz NLC - The Next Linear Collider Project Muon rate in detector ~1000x design goal before adding spoiler walls 4.4E-6 Muons/Scraped e- ** Assumed Halo 1E-3

19. Tom Markiewicz NLC - The Next Linear Collider Project Distributions with No Spoilers at 250 Gev/ Beam Muon HCAL ECAL Tunnel

20. Tom Markiewicz NLC - The Next Linear Collider Project 18m Wall Downbeam of all sources reduces rate by x30 25% from E coll (recall pessimistic 1% spread!) 75% from Betatron coll

21. Tom Markiewicz NLC - The Next Linear Collider Project Donut Toroid Muon Attenuators Well defined source locations followed by at least 5m of free space (at 250 GeV/beam) may be serviced by devoted attenuators –Nice if there is a dipole between the source and the donut Lattice does not always permit this –NLC betatron collimation system has space for 6 5m-long attenuators (SP2/AB2,PC1,SP3/AB3/PC2,PC3,SP4/AB4/PC4,PC5/SP5/AB5) –NLC energy collimation region has no space NLC MuCarlo study uses 120cm diameter donut toroids JLC advocates double donut TESLA uses single donut

22. Tom Markiewicz NLC - The Next Linear Collider Project Donuts reduce Muon rate from Betatron Region rate by x8

23. Tom Markiewicz NLC - The Next Linear Collider Project Additional 9m Wall reduces Betatron  rate by x50 and E Coll  rate by x100

24. Tom Markiewicz NLC - The Next Linear Collider Project Distributions with 2 Spoilers at 250 Gev/ Beam Muon HCAL ECAL Tunnel

25. Tom Markiewicz NLC - The Next Linear Collider Project Radiation Safety Aspect of Collimator System Muons Can you occupy IR2 when IR1 is running? Can you occupy IR1 when IR2 is running? Last studied for 2001 BD model with shared collimation An issue whenever IR2 “sees” IR1 collimators NO 18m wall in IR2 lineIR2 line has 18m wall

26. Tom Markiewicz NLC - The Next Linear Collider Project Muon Dose Rates in IR1 and IR2 when other IR has beam 1.0 TeV CMNo Spoiler18m Mag Spoiler @ z=321m SourceHaloIR1 ( mr/hr) IR2 ( mr/hr) IR1 ( mr/hr) IR2 ( mr/hr) Total for 2 beams 10.90.290.610.15 Total for 2 beams @500 GeV 4.50.130.120.01 If do nothing and halo=10 -3, dose is 10-20x SLAC 0.5 mrem limit 18m mag spoiler buys you x20 to 40; IR2 looks OK in any event Max credible accident only dumps 10 3 more beam, limit is 50E3 higher SLAC Rad Safety Rules: –0.5 mrem/hr for normal operation –25 rem/hr (3 rem max dose) for max credible accident Run MUCARLO and find maximum dose rate in any 80cmx80cm area Simultaneous Occupation OK if Magnetized Wall Is Present

27. Tom Markiewicz NLC - The Next Linear Collider Project Conclusions on Muons Unless the beam halo loss rate is ~10 -6, all collimator designs will need some combination of magnetized spoilers to reduce the muon flux For the case of the NLC design it appears that two magnetized walls serve the purpose. At least one wall per IR per side may be required for personnel protection Current plan is to leave space for the caverns that would enclose these walls but to not install until measurements of halo and muon production sources indicate it is necessary. Judicious use of point muon attenuators may be useful