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