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NLC - The Next Linear Collider Project
Backgrounds UpdateTom Markiewicz
SLAC
LCWS Cornell15 July 2003
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
Tom Markiewicz
NLC - The Next Linear Collider Project
Pair Refresher Course
At 500 Gev w/ NLC beam parameters:• 49.2K e- per bunch @ <E>=4.05 GeV
• 200 TeV Total
• 0.37mWatts per side
Tom Markiewicz
NLC - The Next Linear Collider Project
Pairs Lost on Lum and QDF1
Tom Markiewicz
NLC - The Next Linear Collider Project
Pair Energy Flow
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0 2 4 6 8 10 12
QD0SD0
M1
Pair LumMon
M2
Low Z shield
-0.2
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
0.2
0 2 4 6 8 10 12
QD0SD0
M1
Pair LumMon
M2
Low Z shield
Remaining 81.7% of pairs convert into photons and are absorbed by masks & calorimeters
E dep per bunch (GeV)
Power (mW)
% Total E_dep
% Total Pair
Energy
Peak E dep per
bunch per cc
Power (Watts)
Rads/10^7 sec
LowZ (Be) 1187.87 4.38 3.26% 0.60% 19.22 7.09E-05 3838.808Lum (W) 23585.62 87.05 64.72% 11.83% 138.75 5.12E-04 2653.51QD0 (Fe) 915.22 3.38 2.51% 0.46% 1.72 6.35E-06 80.66752QDF1 (Fe) 10755.11 39.70 29.51% 5.39% 156.19 5.76E-04 7325.267Total 36443.82 134.51 100.00% 18.28%
Tom Markiewicz
NLC - The Next Linear Collider ProjectCollimation System Designed to Make
Detector Free of Machine Backgrounds
E=250 GeVN=1.4E120.1% Halo distributed as 1/X and 1/Y for 6<Ax<16x and 24<Ay<73y with p/p=0.01 gaussian distributed
Tom Markiewicz
NLC - The Next Linear Collider Project
SR at IP due to Halo
X (cm)
Y
X (cm)
Log10(E) (GeV)
Quad
Bend
.3 Ne-<E>=4.8 MeVQuad
Bend
Tom Markiewicz
NLC - The Next Linear Collider Project
X-Y at Spoiler #3
30m x 25m
6x<Ax<16x
24y<Ay<73y
60m x 50m
12x<Ax<32x
48y<Ay<146y
Tom Markiewicz
NLC - The Next Linear Collider Project
Loss Distribution in “Worst Case” Scenario
E=250 GeVN=1.4E120.1% Halo distributed as 1/X and 1/Y for 2*6<Ax<2*16x and 2*24<Ay<2*73y with p/p=0.01 gaussian distributed AND SP/AB/DP x2-x3
1.E-08
1.E-07
1.E-06
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
0 500 1000 1500
z
N 1000x
Tom Markiewicz
NLC - The Next Linear Collider Project
Worst Case Ray Distribution at Spoiler#1
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
Tom Markiewicz
NLC - The Next Linear Collider Project
NLC Beam Delivery thru 1999
-30
-20
-10
0
10
20
30
-6000 -4000 -2000 0 2000 4000 6000
e- e+
Collimation Collimation
Interaction Region 1
IR2
IR Transport = Final Focus
Extraction
Big Bend=10 mrad
Interaction Point 2Protect via distance and “Big Bend”
-5
0
5
10
15
20
25
30
35
40
-2000 -1500 -1000 -500 0 500 1000 1500 2000
e- e+Low E IP
Angle =10 mrad
Hi E IP
Currently 3x shorter & No Bend
Tom Markiewicz
NLC - The Next Linear Collider Project
Layout of Spoilers, Absorbers & Protection
Collimators
Betatron
Betatron Cleanup
Energy
FF
Tom Markiewicz
NLC - The Next Linear Collider Project
Calculated Beam Loss:Input to MuCarlo
Tom Markiewicz
NLC - The Next Linear Collider Project
9 & 18m Toroid Spoiler Walls
4.5m
0.6m0.6m 2cm
BB
170 Tons/m
Design Constraints: Minimize gap & minimize stray field in beampipe
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 line
IR2 line has 18m wall
Somewhat arbitrary Goal: 10 muons / detector / train (from both e-,e+ systems)
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
Tom Markiewicz
NLC - The Next Linear Collider Project
Muon rate in detector ~1000x design goal before adding
spoiler walls4.4E-6 Muons/Scraped e-
** Assumed Halo 1E-3
Tom Markiewicz
NLC - The Next Linear Collider Project
Distributions with No Spoilers at 250 Gev/ Beam
Muon
HCAL
ECAL
Tunnel
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
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
Tom Markiewicz
NLC - The Next Linear Collider Project
Donuts reduce Muon rate from Betatron Region rate
by x8
Tom Markiewicz
NLC - The Next Linear Collider Project
Additional 9m Wall reduces Betatron rate by x50 and E Coll
rate by x100
Tom Markiewicz
NLC - The Next Linear Collider Project
Distributions with 2 Spoilers at 250 Gev/ Beam
Muon
HCAL
ECAL
Tunnel
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 line
IR2 line has 18m wall
Tom Markiewicz
NLC - The Next Linear Collider Project
Muon Dose Rates in IR1 and IR2 when other IR has beam
1.0 TeV CM
No Spoiler 18m Mag Spoiler @ z=321m
Source Halo IR1 (mr/hr)
IR2 (mr/hr)
IR1 (mr/hr)
IR2 (mr/hr)
Total for 2 beams 10.9 0.29 0.61 0.15
Total for 2 beams @500 GeV
4.5 0.13 0.12 0.01
•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 103 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
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
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