the myrrha hebt

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Page 1 L. Perrot, MYRRHA accelerator 1st International Design Review MYRRHA / CDT The MYRRHA HEBT L. Perrot : [email protected] , CNRS-IN2P3-IPNO MYRRHA accelerator 1st International Design Review WP1 - GLOBAL ACCELERATOR DESIGN High-energy beam lines Starting point : - the Central Design Team (CDT) for a fast spectrum transmutation experimental facility (FASTEF), EURATOM, FP7, Grant Agreement N°: FP7- 232527 [1] - Deliverable D2.4 of the WP2, task 4. Accelerator design related issues Authors : J.L. Biarrotte, L. Perrot, H. Saugnac (CNRS), A. Ferrari (HZDR), D. Vanderplassche (SCK-CEN) Outlook : 1. Reference layout 2. Beam dynamic 3. Magnets 4. Beam Instrumentation 5. Mechanical design 6. Shielding and radioprotection 7. Additional issues

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The MYRRHA HEBT. MYRRHA accelerator 1st International Design Review WP1 - GLOBAL ACCELERATOR DESIGN High-energy beam lines Starting point : the Central Design Team ( CDT ) for a fast spectrum transmutation experimental facility ( FASTEF ), EURATOM, FP7, Grant Agreement N°: FP7-232527 [1] - PowerPoint PPT Presentation

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Page 1: The MYRRHA HEBT

Page 1L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT The MYRRHA HEBT

L. Perrot : [email protected] , CNRS-IN2P3-IPNO

MYRRHA accelerator 1st International Design ReviewWP1 - GLOBAL ACCELERATOR DESIGN

High-energy beam lines

Starting point :- the Central Design Team (CDT) for a fast spectrum transmutation experimental facility (FASTEF),

EURATOM, FP7, Grant Agreement N°: FP7-232527 [1]- Deliverable D2.4 of the WP2, task 4. Accelerator design related issues Authors : J.L. Biarrotte, L. Perrot, H. Saugnac (CNRS), A. Ferrari (HZDR), D. Vanderplassche (SCK-CEN)

Outlook : 1. Reference layout2. Beam dynamic3. Magnets4. Beam Instrumentation5. Mechanical design6. Shielding and radioprotection7. Additional issues

Page 2: The MYRRHA HEBT

Page 2L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT Introduction

The Central Design Team (CDT) for a fast spectrum transmutation experimental facility (FASTEF). It is the next step next after FP6 IP-EUROTRANS. European program : 2009-2012.

“FASTEF is proposed to be designed to an advanced level for decision to embark for its construction at the horizon of 2012 with the following objectives: to demonstrate the ADS technology and the efficient transmutation of high level waste; to operate as a flexible irradiation facility; to contribute to the demonstration of the Lead Fast Reactor technology without jeopardising the above objectives”

The Myrrha Accelerator eXperiment (MAX) : http://ipnweb.in2p3.fr/MAX/“To feed its sub‐critical core with an external neutron source, the MYRRHA facility requires a powerful proton accelerator (600 MeV, 4 mA) operating in continuous mode, and above all featuring a very limited number of unforeseen beam interruptions. The MAX team, made up of accelerator and reliability experts from industries, universities and research organizations, has been set up to respond to these very specific twofold specifications.”

CDT = R&D reactor+HEBT MAX = R&D accelerator

The R&D program for the accelerator to MYRRHA ?

We will be focus on the design of the final beam line which aims to transport the 600MeV, 4mA proton beam from the LINAC exit - up to the spallation target located inside the reactor core,- up to the 2.4MW beam dump

Page 3: The MYRRHA HEBT

Page 3L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

HEBT : Transfer line from accelerator to the spallation target Prepare the beam spot requirements (shape, position, intensity and energy) Transfer line from accelerator with the beam-dump Provide a safe operation and maintenance

1. Reference layout

Proton Beam specifications : ; stability to ±1% ; stability to ±2%

Vertical injection «donut-shape» beam footprint on the spallation window with 85mm diameter and stability

to ±10% Reliability : interruptions < 10 longer than 3sec. during a 3 months operation. The

constraint is almost given by yhe accelerator

Page 4: The MYRRHA HEBT

Page 4L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 1. Reference layout

General layout compatible with reactor building produced by Empresarios Agrupados, CDT WP3 (“Plant requirements”) [4]

Beam line to reactor: layout FROZEN Beam line to dump: not fully finish

40m

30m

24m

26.5m

15m

38m downstream the LINAC tunnelZ=-2.5m ground

Reactor

Scanning device

From EUROTRANS [2] project, it was choosen the second conceptual design (less components and lowest high of the reactor building [3].

Dump

MatchingObject point

45° rectangularbending magnet

90° bending magnetPole-face rot.=26.565°

Quad triplet

Quad triplet

Quad

trip

let

20° bending magnet+2 quadrupoles

-45° rectangularbending magnet

Page 5: The MYRRHA HEBT

Page 5L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 1. Reference layout

40m

30m

24m

26.5m

15m

38m downstream the LINAC tunnelZ=-2.5m ground

Reactor

14 quadrupoles (L=0.5m, 100mm, 3T/m max)⌀

2 dipoles 45° (ρ=3.2m, gap 100mm, 22.5° edges) 1 dipole 90° (idem, 26.56° edges, radiation-hard) 18 DC steerers (L=0.3m, 150G max), beam orbit correction 2 AC steerers (L=0.3m, 150G max)

Scanning device

Dump

MatchingObject point

-45° rectangularbending magnet

90° bending magnetPole-face rot.=26.565°

Quad triplet

Quad triplet

Quad

trip

let

20° bending magnet+2 quadrupoles

45° rectangularbending magnet

Pipe aperture = 100mm, in dipole=95mm Diagnostics boxes (in green), see later Beam losses have to be < 1nA/m like SNS [5] for

components activation and safe maintenance Vacuum < 10-7mbar At the target window 10-4 mbar must be achieve

(beam losses ~0.05nA/m)

In case of incident with the beam in the HEBT : Tswitch-

off<50ms.

Diagnostics

Page 6: The MYRRHA HEBT

Page 6L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

By construction, the line: is achromatic at 1st order (position & divergence on target independent of beam energy) : T16=T26=0

from LINAC to target has telescopic properties at 1st order (image size on target = 9 x object size at point 0) : T11=T33=9

between object point and target. Target beam size is control by the beam size at the matching object point 0.

Donut-shape beam footprint achieved with the AC scanning magnets. Circular movement with few tens of Hz

No focusing during the last 25m (reactor hall)

2. Beam dynamic studies

O

QP1-3

QP7-9

QP10-12

QP4-6

Page 7: The MYRRHA HEBT

Page 7L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

Beam phase space at the LINAC exitBeam phase space on the spallation window

Without scanning : RMSX,Y=9mm

600MeV Protons beam envelopes at 3RMS, using TraceWin Code [6]

Normalized emittances: ex=0.242, ey=0.234, ez=0.291 p.mm.mard

Without scanning

Horizontal plane in blue, vertical plane in red T46 vertical dispersion

O

Page 8: The MYRRHA HEBT

Page 8L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

13kW/2.4MW

-- Horizontal -- Vertical

Target aspects: Why do you need the beam scanning ?Beam scanning must be done in order to protect the Pb-Bi target windowBut :No space is involved inside the reactor hall (no quad, no instrumentation)Safety do not permit to install the scanning device after the last 90° dipoleDonut shape is impose by the Pb-Bi liquid target coolingMaximum beam scanning amplitude is fixed by target windows + last 2 meters beam pipe penetration inside the reactor coreScanning speed depend almost to target windows and Pb-Bi speed cooling

Need to 2 scanning dipoles located before the last 90° vertical dipole the maximum amplitude have to be less than 150G with frequency close to 100Hz (not yet frozen)

The scanning devices not yet design

25m

Reactor

Scanning

2. Beam dynamic studies

Beam phase space on target with scanning

Target window zone

Page 9: The MYRRHA HEBT

Page 9L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

Impact of a energy jitter The beam target foot-print have to be not

sensitive to primary beam energy variation, which is ensure by the first order achromatic line

But between dipole, beam shift centroide is dependant to T16. Therefore, dedicated instrumentation have to be install like collimators, ring losses or segmented collimators.

X Plane

Y Plane

Collimators / rings

Collimators / rings

Effect of a 0.5% beam shift energy(3MeV / 600MeV)

Target window zone

Beam spot movement

“donut-shape” footprint Use to a raster magnets on X and Y, using

a (possibly redundant) set of fast steering magnets operated at frequencies of several tens of Hz

Central trajectory is continuously deviate. The ±9 mm RMS beam spot on target is moved around the window centre in a circular pattern of radius 20 mm.

Octupole expander solution is not feasible (see next slide)

Page 10: The MYRRHA HEBT

Page 10L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Multipole beam expander ?

Homogeneous beam density distribution can also be performed using a set of octupole magnets in front of the target:

- The first set of octupoles (1 or 2) produces a square homogeneous footprint- An additional turned octupole transforms the square in circle

=> For MYRRHA, it seems extremely complicated (if not impossible) to implement

This is a beautiful solution, but several drawbacks:- Produces a lot of beam halo => has to be located near the final target

1. Impossible in our case2. Tested location: upstream. Unmanageable (unless a possible 2nd order O-I

system ...?) - Extremely sensitive to any beam misalignment or beam size variation

2. Beam dynamic studies

120m

m

60m

m

Page 11: The MYRRHA HEBT

Page 11L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Tuning method :

1. Set the magnets to their theoretical value, & send a very low duty cycle beam (10 -4)

2. Adjust DC steerers for orbit correction (alignment)

3. Adjust QP1-3 => tune beam waist on 0 w/ desired size (1mm rms), using 3 transverse beam profil detectors

4. Adjust QP7-13 => achromaticity optimization using beam position monitor, target optical diagnostic.

5. Adjust QP 4-6 => re-adjust desired beam size on target (9mm rms), check telescopic properties

6. Recheck alignment & switch on + tune scanning device for obtain the “donut-shape” on target

7. Increase step by step the beam duty cycle (chopper in the LEBT)

2. Beam dynamic studies

O

QP1-3

QP7-9

QP10-12

QP4-6

Page 12: The MYRRHA HEBT

Page 12L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

Statistical error study• Static errors are randomly applied to:

- Magnets (displacement, field error)- Input beam (position, divergence, energy, emittance, intensity, mismatch)

• The beam tuning procedure is simulated step by step:- static errors are corrected when possible - errors on beam diagnostics measurements are taken into account

• Dynamic errors (mechanical vibrations, stability... ) are then randomly applied: - These transient errors are not corrected- Applied to magnets (displacement, field error) & input beam (position, divergence, energy,

emittance, intensity, mismatch)

• Iteration is performed to get good statistics: - 100 different line configurations- each one with a tracking involving 105 macro-particles

Page 13: The MYRRHA HEBT

Page 13L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

1. Nominal 99% envelopes without errors, without scanning

Error calculations

Page 14: The MYRRHA HEBT

Page 14L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

2. 99% envelopes with UNCORRECTED static errors (random distribution) , without scanning

Error calculations

Page 15: The MYRRHA HEBT

Page 15L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

3. 99% envelopes with CORRECTED static errors (same random distribution) , without scanning

Error calculations

Page 16: The MYRRHA HEBT

Page 16L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

4. 99% envelopes with CORRECTED static errors + uncorrected dynamic errors, without scanning

Error calculations

Page 17: The MYRRHA HEBT

Page 17L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 2. Beam dynamic studies

Possible losses on collimator:- Min = 0, Max = 29kW

- Mean = 0.3 kW, RMS = 3kW

=> Losses in 1% cases

Losses on final tube:

- Min = 0.5kW, Max = 110kW

- Mean = 15 kW, RMS = 14kW

from 107 particles

Error calculations: beam losses

Page 18: The MYRRHA HEBT

Page 18L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Mean orbit (X) Mean orbit (Y)

RMS orbit (Y)RMS orbit (X)

Error calculations: trajectories

2. Beam dynamic studies

This error study is quite insufficient to get to definitive conclusions, but gives already good orders of magnitude for the required tolerances and a good feeling of the general situation. We need a end-to-end accelerator errors calculation

Page 19: The MYRRHA HEBT

Page 19L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

X rms size Y rms size

Footprint (log scale) Footprint (linear scale)

Error calculations: target footprint : fluctuations are considered acceptable

2. Beam dynamic studies

Page 20: The MYRRHA HEBT

Page 20L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Error calculations: sensitivity

2. Beam dynamic studies

• Errors impacting the orbit excursion through the line (i.e. beam losses)1. Beam energy jitter: ±1MeV => 5 mm rms deviation (DYNAMIC)2. BPM precision: ±0.5mm => 2 mm rms deviation (STATIC)3. Magnets alignement: ±0.3mm => 1 mm rms deviation (STATIC)4. Dipole field stability: ±2.10-5 => 0.5mm rms deviation (DYNAMIC)

• Errors impacting the position on target1. Input beam divergence jitter: ±0.01mrad => 0.7mm rms (DYNAMIC)2. Input beam position jitter: ±0.1mm => 0.6mm rms (DYNAMIC)3. Dipole field stability: ±2.10-5 => 0.5mm rms (DYNAMIC)4. Quadrupoles mechanical vibrations: ±10mm => 0.4mm rms (DYNAMIC)5. Beam energy jitter: ±1MeV => 0.3mm rms deviation (DYNAMIC)6. Dipole mechanical vibration (Y): ±10mm => 0.2mm rms (DYNAMIC)

• Errors impacting the spot size on target1. Quadrupoles gradient stability: ±10-3 => 0.15mm rms (DYNAMIC)2. Beam energy jitter: ±1MeV => 0.1mm rms (DYNAMIC)3. Beam profiler precision measurement: ±0.5mm => 0.1mm rms (STATIC)

Page 21: The MYRRHA HEBT

Page 21L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Beam line to dump

• Present layout of the line: 20° dipole to avoid neutron back

streaming & ease the maintenance 2 quadrupoles to defocus beam on dump

with 210mm diameter 240mm larger beam vacuum pipe along

the final 6m

• Beam dump design Preliminary design from the

1 MW PSI proton dump (larger) Required shielding, preliminary study

performed Detailed mechanical & thermal

assessments to be done Power losses = 2-3kW/cm² 600MeV protons range in Copper = 25cm

2. Beam dynamic studies

15m

Tuning the beam line from p-source up to HEBT (commissioning, tuning & check)

3s beam envelops

Page 22: The MYRRHA HEBT

Page 22L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Quadrupoles

3. Magnets

2 series of quadrupoles : 14 for the beam main HEBT line (Q-50), 2 for the beam-dump line (Q-100) Quadrupole design & size choose for minimize fringe fields & others higher orders contribution Current density from 2 up to 10 A/mm² Water cooling < 10 bars Radiation-hard materials (low carbon steel)

Design can be closed to the SNS quadrupoles

Page 23: The MYRRHA HEBT

Page 23L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Dipoles

3. Magnets

600MeV protons => Br=4 Tm => Dipole radius = 3.2m 4 magnets 3 angles of deviation : 20° (beam-dump line), 45° (x2) and 90° (up to reactor) C-type magnets (except for 20° magnet) Reliability have to be taking into account (coils design) Radiation-hard materials especially for 90° and 20° magnet

Design can be closed to the CNAO cancer therapy facility in Italy [7]

POISSON calculation of a basic 90° dipole magnet for MYRRHA/FASTEF. 2. 10-4 Field homogeneity is achievable in the “good field region”.

Page 24: The MYRRHA HEBT

Page 24L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Steering and scanning magnets

3. Magnets

Steering magnets are used for the orbit correction DC power supply Number = 18 (9 for horizontal plane, 9 for vertical plane) Magnetic length = 30cm Aperture = 110mm Working range : -500G<B<500G RMS operating value = 85G

Scanning magnet : produce the beam «donut-shape» on the Pb-Bi window AC power supply Number = 2 (X&Y) or 4 for redundancy Magnetic length = 30cm Aperture = 110mm Working range = -150G<B<150G Frequency : to be defined (~few hundreds of Hertz)

Orbit correction DC steerer used at the CNAO facility (Italy)

Prototype of a 500 Hz 500G scanner magnet developed at Los Alamos for the APT project [8]

Page 25: The MYRRHA HEBT

Page 25L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Overview

4. Beam Instrumentation

Beam diagnostics and control systems will be deployed all along the final beam transport line in order to tune the beam, maintain normal operation according to specifications, and protect the beam line equipments in case of malfunctioning.

Main beam diagnostic devices along the HEBT

beam intensity measurement current monitors (accuracy <1%), beam loss monitors for trigger interlocks for beam switch off (DT<1ms) Optical system (VIMOS like system at PSI [9] for beam footprint on target monitor and survey. For MYRRHA, need a

dedicated R&D Couple of halo scrappers and wire profilers should also be used if possible (this will probably not be the case) in the last

straight section for redundancy. At the exit of the 90° bending magnet, halo monitors for checking the beam center and size are roughly correct. Standard beam diagnostics (position and size)

Diagnostics type and usage for beam transfer line

Page 26: The MYRRHA HEBT

Page 26L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Few details

4. Beam Instrumentation

PSI BPM: capacitive pick-ups or magnetic loops symmetrically arranged in the pipe wall

Energy : ToF technique = 3 pick-up capacitive electrodes

L=20 needed to obtain ( / )<10-3 𝜕𝐸 𝐸

SPIRAL2

Beam profiler : electron secondary emission or wire scanner

SPIRAL2

PSI

Current : fundamental for the reactor monitoring

SPIRAL2

PSI

TM01-mode coaxial resonator (aluminum, with a 10μm coating layer of silver to improve the electrical conductivity)

DCCT : average beam current

ACCT : single bunch monitoring

Halo & Losses : tuning phase + safety (machine protection) : <1nA/m loss level

SPIRAL2PSI ionisation

chamber

Loss Ring : particle interactions induce currents, size adapted to the beam size, material Cu, Ni, Mo or C, cooling may be necessary, sub-sections can be useful

BLM : detectors implantation around the beam tube. 6 along the HEBT to ensure the 1nA/m loss level

Target monitoring : measure the beam size + position close the target. Crucial & challenging measurement for MYRRHABeam have to be monitored continuously (deviation from tight reference values and peak power density feed-back).Optical technic like VIMOS (at SINQ - PSI) or TIS (SNS):

- Thermal incandescence- Cr/Al2O3 fluorescence- Optical transition radiation (OTR)- He fluorescence (from fill gaz in line)

Page 27: The MYRRHA HEBT

Page 27L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 5. Mechanical design First conceptual design of the whole high energy part of the line and its integration inside the reactor

building. We take into account the design of the reactor and the definition of the building Separated in different parts, due to the various security constraints Safety requirements have an important impact on the building design, the accessibility and the

mounting/dismounting procedures

Page 28: The MYRRHA HEBT

Page 28L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 5. Mechanical design

Part 1 :- beam axis =+1.5m to the floor- Corridor 5m large- Beam line not centered (3m right) for accessibility- No crane- alignment done with “Laser Tracker”

Part 2 :- 45° inclined line, length = 30m- Part of the beam dump casemate in this hall- Crane of 50 tons capacity- BD line in a 20° deviation. Reduction of the neutrons

backscattering and better access for the handling

Part 3 :- Tunnel of 22 metres long, 6.5 metres large and 10

metres height- Crane of 50 tons capability, common with part 2

10-7 mbar vacuum specification (not yet study) : Vacuum components and fittings will be ConFlat® type Turbo-molecular pumping group with 200 l/s capacity. 1 pump placed each 3m.

Each component subjected to alignment adjustments (magnets, diagnostic boxes, collimators…) has to be installed using bellows allowing enough longitudinal and lateral displacement.

Page 29: The MYRRHA HEBT

Page 29L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT 5. Mechanical design

Part 4 : 90° magnet zone- Backscattered neutrons from reactor => hot cell probably- Need to specific material, remote handling and nuclear waste

capabilities- Pumping system of the vertical line & 90° dipole will be in

this section (200l/s turbo + 16m3/h primary)- 50 tons crane- Fast valve before and after concrete wall - Vertical port for beam foot-print detection system and/or

neutron dump coming from reactor.

Part 5 : Beam line inside the reactor hall- High activation zone.- Need complete isolation, full remote and lateral

handling.- Less active components must be chosen- Reactor access imposed to dismount the line- No pumping system in this section

3 parts for the line Alignment is a major concern Vacuum at the spallation window fixed to 10-4mbar 2 Fast valves (15ms closing time) for protection against

the window breaking and accelerator failure (like cryogenic accidents)

Page 30: The MYRRHA HEBT

Page 30L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

The beam dump casemate=Hot cell15 m deep, concrete wall to 5m thickness, 20 tons crane

10 m

30 m

9 m

A 2.4 MW, full power beam dump, based on the 1.2 MW PSI proton beam dump, is foreseen to allow the commissioning of the MYRRHA accelerator independently from the reactor.The conceptual design of the MYRRHA beam-dump is taken from the 1.2MW PSI existing dump [10].Dump is handled from the top using the common 50 tons crane (part 2 & 3).Due to the 20° deviation. It is not necessary to dismount the line. Beam power deposition on 6 blocks (PSI=4 blocks), length=3mMaterial : Copper but need to be optimized considering the high level of activation. High density carbon fiber surrounded by stainless steel can by a useful alternative

5. Mechanical design

Part 6 : Beam line casemate: Conceptual design

Structure of the 1.2 MW PSI proton beam dump

Page 31: The MYRRHA HEBT

Page 31L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

The goal of the shielding design is to guarantee that, under normal operational conditions, the added integrated dose to anybody working around the FASTEF/MYRRHA accelerator is extremely small, i.e. comparable or smaller than the natural background. To reach this goal one must rely on: the use of conservative beam loss assumptions; the use of a conservative shielding model; the assumption of an occupancy factor = 1, that means 2000 hours/year occupancy close to the outer

shielding wall (at the maximum dose rates).First evaluations have been performed during the PDS-XADS project, considering a continuous 1 nA/m proton loss at

600 MeV. This is equivalent to a mean beam loss level of about 0.6 W/m.

6. Shielding and radioprotection

Required concrete/earth combined thickness at 600 MeV to reach the 0.5 μSv/h dose rate level.

For 600MeV protons Shielding issues in the reactor building impact strongly on the 90° dipole shielding. Concrete walls and roofs up to 5 m thick would therefore be needed to reach the 0.5 μSv/h dose rate outside the facility.

Shielding issues around the beam dump : the BD design must satisfy the shielding requirements & minimize the backscattered neutron & minimize the BD activation

Page 32: The MYRRHA HEBT

Page 32L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Main problems : Activation of the elements devoted to the beam absorption (beam dump) Activation of the material of the line due to beam lossesCalculations preformed using the FLUKA MonteCarlo code [11] which give :- Particle fluences- Ambient dose equivalent- Time evolution of the activation products (build-up and decay of radionuclides)

6. Shielding and radioprotection

Activation

Neutron fluence (n/cm2 per beam proton) in and around the target

Calculation on various “targets” (Carbon, Copper, AlSl-316L, Aluminium, Iron)

Residual dose rate around the carbon target, at different cooling times

Residual (in μSv/h) around 100 m beam-line, for two representative cooling times after a short and a long-term irradiation.

Page 33: The MYRRHA HEBT

Page 33L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

Full absorption of the 600MeV protons beam

We have already presented a structure closed to the 1.2MW PSI beam-dump. Advantage of the know how but secondary neutrons and activation are very high.

We have explore an alternative solution for the safety studies with a soft material as dump core (Carbon) surrounded by a high-Z shielding structure (stainless steel). Smaller neutron yield and less activation problems.

6. Shielding and radioprotection

Optimisation of the beam dump zone

Neutron fluence (n/cm2 per primary proton)in the dump concrete cage of the dump casemate

Copper core Carbon core +stainless steel

Dose rate (in mSv/h)

Copper core

Carbon core +stainless steel

The soft Carbon core solution is clearly a good candidate

Beam dynamic and mechanical integration not yet study

Page 34: The MYRRHA HEBT

Page 34L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

The building detailed definition is still in progress, and will probably keep moving slightly until the start of the MYRRHA construction. It is therefore important to ensure that the beam line layout will be able to adapt to these changes as much as possible without major consequences.

7. Additional issues

Adaptation of the final layout

Possible beam line adaptations in the case of a reactor height increase

Study of a radiatively cooled cold window

Vacuum protection of the final beam line in case of a target window failureThird passive protection in addition to the fast valves : use a thin metallic foil able to sustain high temperature gradients without perturbing too much the beam optics. In existing (low-power) accelerators, titanium foils of a few hundreds of μm are typically used.Study of a 100mm diameter 400mm thick Titanium using LISE++ code [12]. Eloss=0.33MeV, Ploss=1.3kW => fusion of the window (need to have a 30cm beam size (including halo) which is not reasonable.Using a cold window seems to be quite unrealistic

Study of a water cooled cold window

J-PARC ESS prototype

SNS/JPARC : Inconel 718 (1.5 to 2 mm thickness) separated by a 1.6 to 3 mm gap in which water flows (at typically 10 bars) ESS project : Aluminum tube cooled by Helium at 40 bars

Apply to our case with the SNS/JPARC solution, Ploss=27kW Beam emittance increase by a factor 10 (sx’,y’ from 0.4mrad up to 4mrad) => not

compatible with a window location at 25m up to the spallation window Activation of this cold window Need to be located very near the target itselfSNS feedback can be an extremely important issue for MYRRHA

Page 35: The MYRRHA HEBT

Page 35L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

The goal of the MYRRHA/FASTEF final high‐energy beam line is to safely inject the proton beam onto the spallation target located inside the reactor

Consolidated design of the beam line to reactor achieved AC steering magnets are preferred for the beam scanning Error study shows very robust behavior (sensitivity in the X-plane may be optimised) Need start-to-end error studies Near-target optical device appears to be mandatory to be able to correctly tune and monitor the beam

shape on target. First detailed mechanical design is described for each part of the line First shielding and activation calculations have been performed Beam dump design on-going, need to be study in details (structure…)

ConclusionHEBT for the MYRRHA project

A beam line from the LINAC up to the reactor

Page 36: The MYRRHA HEBT

Page 36L. Perrot, MYRRHA accelerator 1st International Design Review

MYRRHA / CDT

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