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

NLC - The Next Linear Collider Project
Backgrounds Update
Tom Markiewicz
SLAC
LCWS Cornell
15 July 2003
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
E dep per
bunch
(GeV)
LowZ (Be)
Lum (W)
QD0 (Fe)
QDF1 (Fe)
Total
Power
(mW)
1187.87
23585.62
915.22
10755.11
36443.82
4.38
87.05
3.38
39.70
134.51
% Total
E_dep
3.26%
64.72%
2.51%
29.51%
100.00%
% Total
Pair
Energy
0.60%
11.83%
0.46%
5.39%
18.28%
Peak E
dep per
bunch per
cc
19.22
138.75
1.72
156.19
Power
(Watts)
Rads/10^7
sec
7.09E-05 3838.808
5.12E-04 2653.51
6.35E-06 80.66752
5.76E-04 7325.267
0.2
0.15
M1
M2
0.1
Remaining 81.7% of pairs
convert into photons and are
absorbed by masks &
calorimeters
SD0
QD0
Low Z
shield
0.05
0
-0.05
-0.1
Pair LumMon
-0.15
Tom Markiewicz
-0.2
0
2
4
6
8
10
12
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<Ax<16sx
and
24<Ay<73sy
with
Dp/p=0.01
gaussian
distributed
Tom Markiewicz
NLC - The Next Linear Collider Project
SR at IP due to Halo
Quad
Ng=7.3 Ne-
Quad
<Eg>=4.8 MeV
Bend
Log10(E) (GeV)
Y
Bend
X (cm)
X (cm)
Tom Markiewicz
NLC - The Next Linear Collider Project
X-Y at Spoiler #3
30mm x 25mm
60mm x 50mm
6sx<Ax<16sx
12sx<Ax<32sx
24sy<Ay<73sy
48sy<Ay<146sy Tom Markiewicz
NLC - The Next Linear Collider Project
Loss Distribution in “Worst Case” Scenario
1.E-01
E=250 GeV
1.E-02
N=1.4E12
1.E-03
0.1% Halo
distributed as 1/X
and 1/Y for
2*6<Ax<2*16sx and
2*24<Ay<2*73sy
with Dp/p=0.01
gaussian
distributed AND
SP/AB/DP x2-x3
N
1.E-04
1000x
1.E-05
1.E-06
1.E-07
1.E-08
0
500
1000
1500
z
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
NLC Beam Delivery Magnet Layout
30
IR2
Protect via
distance and
“Big Bend”
Extraction
Interaction Point 2
20
10
Coll:eIRT1:eColl:e+
IRT1:e+
IRT2:eIRT2:e+
Ext1:eExt1:e+
Ext2:e+
Ext2:e-
Big Bend=10 mrad
e+
e0
-6000
-4000
-2000
0
2000
Collimation
4000
6000
Collimation
Currently
3x shorter
& No Bend
-10
40
IR Transport = Final Focus
35
Low E IP
e-
e+
30
25
20
15
-20
10
5
Angle =10 mrad
0
-2000
Interaction Region 1
-30
-1500
-1000
-500
0
500
Hi E IP
1000
1500
2000
-5
Tom Markiewicz
NLC - The Next Linear Collider Project
Layout of Spoilers, Absorbers &
Protection Collimators
Energy
Betatron
FF
Betatron Cleanup
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
0.6m
0.6m
2cm
4.5m
B
B
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
Somewhat arbitrary Goal: 10 muons / detector / train
(from both e-,e+ systems)
IR2 line has 18m wall
NO 18m wall in IR2 line
Tom Markiewicz
NLC - The Next Linear Collider Project
Muon Yield
For 250 GeV
pm>1 GeV/c
m/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 walls
** Assumed Halo 1E-3
4.4E-6 Muons/Scraped e-
Tom Markiewicz
NLC - The Next Linear Collider Project
Distributions with No Spoilers at
250 Gev/ Beam
Muon
Tunnel
HCAL
ECAL
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
JLC advocates double donut
TESLA uses single donut
• 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
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 m
rate by x50 and E Coll m rate by x100
Tom Markiewicz
NLC - The Next Linear Collider Project
Distributions with 2 Spoilers at
250 Gev/ Beam
Muon
Tunnel
HCAL
ECAL
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
IR2 line has 18m wall
NO 18m wall in IR2 line
Tom Markiewicz
NLC - The Next Linear Collider Project
Muon Dose Rates in IR1 and IR2
when other IR has beam
Simultaneous Occupation OK if
Magnetized Wall Is Present
•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
1.0 TeV CM
Source
No Spoiler
Halo
IR1
IR2
18m Mag Spoiler @
z=321m
IR1
IR2
(mr/hr)
(mr/hr)
(mr/hr)
(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
Markiewicz
•Max credible accident only dumps 103 more beam, limit is 50E3Tomhigher
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
Tom Markiewicz