considerations for an spl-beamdump thomas otto cern in collaboration with elias lebbos, vasilis...
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Considerations for an SPL-Beamdump
Thomas OttoCERN
in collaboration withElias Lebbos, Vasilis Vlachoudis (CERN)
and Ekaterina Kozlova (GSI)
Partly supported by the EC under Framework Programme 7 (sLHC-PP)
Beam specificationPurpose Beam parameter (at E = 5GeV)
Commissioning 1.5 E14 protons pulse-1
0.1 Hz1 E20 protons over 5 months
Annual Set-Up +Machine Development
2 weeks year-1 + 8 hours week-1
1.5 E14 protons pulse-1, 0.1 Hz2.5 E19 protons year-1
Emergency abort 1.5 E14 to 7.5 E15 protons s-1 for very short duration
Thomas Otto SPL Dump SPL – ESS WorkshopLund, 30. 6. – 2. 7. 2010
2
Dump Core: where the energy goes Originally developed for
project X at Fermilab Layered graphite-
tungsten core in a water-cooled aluminum-shell
Power density (W cm-3)
for 1.5 E13 protons s-1
AlC WairThomas Otto SPL Dump 3
Avg. Power density along beam axis (W cm-3)
Assuming 1.5×1014 protons/pulse and 1 pulse every 10s
CORE TUNGSTEN IRON
Thomas Otto SPL Dump 4
Dump shield:containing the secondaries Tungsten shell Iron block External concrete layer Total size:
L = 300 cm W = H = 200 cm
W
Fe
Concrete
Power density (W cm-3)
for 1.5 E13 protons s-1
(different colour scale from last page)
Absorbed dose – does equipment survive ?
Thomas Otto SPL Dump SPL – ESS Workshop Lund, 30. 6. – 2. 7. 2010 6
GykgJ
dmdD
2 m upstream from dump, D ≈1 Gy h-1.Could be a problem for highly integrated electronics, semiconductor detrectors , ...
And the public road ??
Dump location
17 Sv/h
Dump Air Wall Earth
Factor 10 m-1
7 m of earth will reduce H*(10) to 1.7 Sv h-1
Public area with low frequentation: H*(10) < 2.5 Sv h-1 required 7
SvkgJ
QDH
Estimating activity and decay Monte-Carlo Radiation Transport + Nuclear Model
Activation estimates Dose rate estimates (from decay of the radionuclides)
Predictions depend critically on Quality of the nuclear model Representation of materials in the code
The sensitivity of the predictions on these parameters is not always clear
Take as a guideline, allow for safety factors
Thomas Otto SPL Dump 8SPL – ESS Workshop Lund, 30. 6. – 2. 7. 2010
Maintenance in the tunnelAmbient dose equivalent
rate H*(10) after the commissioning run (worst case)
2 m upstream from dump:H*(10) ≈ 100 mSv h-1 (1 day)
≈ 1 mSv h-1 (2 weeks)
H*(10) (Sv h-1)After 1 day
After 2 weeks
Thomas Otto SPL Dump 9SPL – ESS Workshop Lund, 30. 6. – 2. 7. 2010
Tunnel wall and earth:protecting the environment Here, insertion in a
4.4 m wide tunnel 40 cm concrete wall Several metres of earth
“Stars” (inelastic interactions), leading to activation of matter surrounding the dump
Profile of activity concentration in earth: exponential decline 10
Soil activation Soluble radionuclides: H(100%) 22Na (20%) Activation build-up and
decay:
In equilibrium: Production = Activity
Conservative: equilibrium reached only after many years !
tnNtn
nnNdtdn
radettprad
radradettprad
exp1arg
arg
radradradettp annN arg
Thomas Otto SPL Dump
Conservative estimate of Aeq
Average proton intensity2.5 E19 y-1 ≈ 8.13 E11 s-1
3 m “activation” layer around accelerator
All activity diluted only in soil humidity(very conservative)
Result for water sample:3H: 2.4 kBq l-122Na: 100 Bq l-1
Comparison with limits: Drinking water:
28 l exceed radioactivity limit
Don’t source close to SPL Waste water: (ingress in
tunnel)3H o.k. 22Na: Factor 3
Covered by conservativism of model
Thomas Otto SPL Dump 12SPL – ESS Workshop Lund, 30. 6. – 2. 7. 2010
Summary / Conclusions Dump for commissioning and set-up Dump core design “borrowed” from FNAL Absorbed dose and ambient dose rate from
activation: avoid sensitive equipment a few metres upstream Critical operation: repair of dump cooling system
Soil activation: Don’t source drinking water close to accelerator Water ingress (waste water o.k.) Public protected from stray radiation
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