Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 1 Norbert Tesch , A. Leuschner, M. Schmitz, A. Schwarz Deutsches Elektronen-Synchrotron (DESY), Hamburg, Germany ICRS 10 / RPS 2004 – Madeira – 13 th May 2004 A. Introduction B. Thermal Aspects C. Radiolysis and Pressure Waves D. Shielding and Activation E. New Idea: Gas Dump Design Studies for an 18 MW Beam Design Studies for an 18 MW Beam Dump at the future e Dump at the future e + + e e - - Linear Linear Collider TESLA Collider TESLA
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Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 1 Norbert Tesch, A. Leuschner, M. Schmitz,
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Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 1
Norbert Tesch, A. Leuschner, M. Schmitz, A. Schwarz
C. Radiolysis and Pressure WavesC. Radiolysis and Pressure Waves
D. Shielding and ActivationD. Shielding and Activation
E. New Idea: Gas DumpE. New Idea: Gas Dump
Design Studies for an 18 MW Beam Design Studies for an 18 MW Beam Dump at the future eDump at the future e++ee-- Linear Linear
Collider TESLACollider TESLA
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 2
A.1 TESLA Linear ColliderA.1 TESLA Linear Collider
Length 33 km
Earth cover 10-30 m
Particle types electron/positron
Maximum Energy 400 GeV
Luminosity 5.8 1034 cm-2s-
1
Electrons per bunch train
6.8 1013
σx=σy 0.55 mm
Bunch train length 860 s
Repetition rate 4 Hz
Energy per bunch train
4.4 MJ
Total power per beam 18 MW
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 3
A.2 Water Beam DumpA.2 Water Beam Dump
Problem: How to dump 18 MW? Solid, fluid or gas based beam dump? Solid dump: graphite-copper-water dump with heat conduction from copper to water Even with a fast sweeping system (needed to distribute the energy) the solid option was
not practicable for the given beam power in terms of heat extraction Therefore the base line design was the fluid (water) dump option !
Thermal Aspects
Heat extractionexternal / internal
Problems to be addressed:
Other Processes
Radiolysis Pressure waves
Radiation Handling
Shielding
Activation Dismantling and disposal
of activated material @ final shut down
The basic parameters of the water beam dump
Cylindrical H2O volume with L=10 m, Ø=1.5 m and p=10 bar Tboil=180°C
Fast (within bunch train) circular sweep with Rfast= 8 cm needed to avoid local boiling
Not considered here: beam window (vacuum/water, huge design effort!!!) and beam pipe
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 4
water-system
air treatment
water-dump vessel
dump shielding
containment shielding
commissioning beam spent beam
hall
basin
exhaust / chimney
sand
generalcooling water
A.3 Schematic Layout of Water Beam DumpA.3 Schematic Layout of Water Beam Dump
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 5
source: S = 1/860s dE/dV for 0 t 860s and S = 0 otherwise
CFD code Fluent 6.0 without handling of phase transition
AssumptionsAssumptions
e-z
in water: pmax 3.7bar near z-axis @ 100s
pmin -1.6bar near z-axis @ 950s
reduces boiling temp. & solubility of gases !!!
at vessel cylinder: pmax 1.8bar @ 650s
at front/rear face (windows): pmax 0.5bar
pressure wave decay to 0 after 3ms (<<250ms)
400GeV, =0.55mm, 8cm fast sweep
75cm10bar, 50°C
vsound1.5km/s
r
10m
ResultsResults
r [cm]
p [bar]
0 10 30 40 50 60 7020 75
0
3
1
2
p(r) @ z=2.5m0 t 800s
p(r) @ z=2.5m0 t 800s
10 50 100 150 200400
300
500700
800600
r [cm]
p [bar]
0 10 30 40 50 60 7020 75
-1
2
-2
1
0
p(r) @ z=2.5m0.8 t 1.6ms
p(r) @ z=2.5m0.8 t 1.6ms
t [s]
0.8
1.0
0.95
0.9
1.11.2
1.31.4
1.51.6
t [ms]
Pressure if close to boiling temperature
(imperfect beam with 6mm, no sweep, after 325s)
in water: pmax 9bar, pmin -6bar
at vessel cylinder: pmax 2.7bar
at front/rear face (windows): pmax 0.5bar
pressure wave decay to 0 after 20ms* calculations done by TÜV-Nord Gruppe
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 11
C.2 RadiolysisC.2 Radiolysis
H2O cracked by shower of high energy primary electron
net production rate at 20°C and 10 bar: 30 ml/MJ H2 and 15 ml/MJ O2 corresponding to 0.27 g/MJ H2O with spatial distribution according to dE/dV profile
solubility in water at 60°C: H2: 16 ml/l and O2: 19.4 ml/l
FundamentalsFundamentals
18 MW: 4.8 g/s H2O cracked whole primary water (30m3) would be radiolysed in 72 days !
- main contributor to local dose rate, assume equal distribution in water system
300mSv/h at surface of component and 50mSv/h in 50cm distance ! (after 5000h)
- accumulation in resin filters, but also adsorption on circuit surfaces (esp. heat exchanger)
local shielding needed !
2cm thick stainless steel dump vessel gives 400mSv/h on its axis (5000h and 1 month cooling)
regular inspection of vessel (welds, ...) seems to be problematic !
* calculations done with FLUKA code
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 13
D.2 Radiation HandlingD.2 Radiation Handling
Activation of containment air* 18MW, 3000m3 air
necessity of closed containment, „closed“ under-pressure
by continuous exchange rate of 1vol/h and controlled exhaust
looks fine except for short lived isotopes: need „delay line“ of about 1 hour !
Asat A(5000h) A_specific(5000h) [Bq/m3]
w/o air exchange
with air ex-change 1vol/h
allowed limit
3H 1.4GBq 43MBq 14 000 3 1 000
7Be 390MBq 370MBq 120 000 70 6 000
z
containment air
2m2m
2m
10m
5m5m
5m
dump20cm steel +1.8m concrete
r exhaust
Scheduled opening of primary circuit 30m3 water, 100TBq of 3H
flush water into storage tank, 100l remain (0.1mm on 1000m2), vent system with dry gas
via 95% efficient condenser 5l 10GBq tritium have to be released to outside air
meeting the limit of 1kBq/m3 needs venting with 107m3 air this takes 1000h=42days with 104 m3/h using a chimney is necessary
(acceptance!)Dismantling of activated system after final shut down after 20 years, 200TBq of 3H
primary water solidifying as concrete 5000 barrels (200l, 40GBq)
steel components (150t, 106Bq/g) & concrete shielding (1500t, 200Bq/g) = a lot of M€
* calculations done with FLUKA code
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 14
E.1 New Idea: Gas DumpE.1 New Idea: Gas Dump
Problems and disadvantages of water dump: High tritium production (to reduce: larger atomic number of dump material) Critical window design, 10 bar static + 0.5 bar dynamic (reduce pressure) Radiolysis, local and instantaneous effects represent a severe risk
(to avoid: one-atomic gas) Handling of water during maintenance and final shutdown (less tritium) Disposal costs not negligible (less tritium)
To overcome most of the problems and disadvantages
the following gas beam dump was proposed: Material: Noble gas (first attempt: Argon @ 1 bar)
in inner tube (r=4 cm) acts as scattering target, (energy deposition of 0.5 %) and distributes
the beam energy longitudinally (no sweeping) Main part of the energy is dumped in Iron shell
of radius 52 cm (average power loss 18 kW/m) Surrounded by 4 cm thick Water cooling system Dump system has diameter of 1.20 m and length of 1000 m Can be used as - dump as well
tunnel
gas dump
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 15
E.2 Gas Dump: Energy DensityE.2 Gas Dump: Energy Density
Energy density in GeV/cm3 in r-z view for one 400 GeV electron*
Energy Density [GeV/cm3]
length [m]
radius [cm]
Argon
I ron
Water
Air
Energy Density [GeV/cm3]
length [m]
radius [cm]
Energy Density [GeV/cm3]
length [m]
radius [cm]
Argon
I ron
Water
Air
* calculations done with FLUKA code
Norbert Tesch (DESY) – Design Studies for an 18 MW Beam Dump at TESLA – ICRS 10 / RPS 2004 – Madeira – May 2004 16
E.3 Gas Dump: ComparisonE.3 Gas Dump: Comparison
Disadvantages of gas dump: Length of dump inside collider tunnel Space for additional shielding needed
adopted tunnel design necessary Not easy to reach constant energy density of 18 kW/m over whole length
Conclusion:
The fluid (water) beam dump seems to be feasible, but with severe disadvantages !!!
The gas (argon) beam dump option seems to be a very attractive alternative and will surely be considered in an early design stage of the next linear collider !!!
Water Dump Argon Dump
Asat Tritium 250 TBq (in water)
29.3/0.7/0.02 TBq (in iron/gas/water)
Beam Window10 bar static and 0.5
bar dynamic, size 20 cm1 bar static and 0.01
bar dynamic, size 8 cm
Radiolysis see above none
Advantages of gas dump: Tritium production Beam window Radiolysis Maintenance and disposal Cases of emergency Acceptance and permission !!!