Proposal for a programme of Neutrino Factory R&D

Introduction

Bath, RMCS Shrivenham, Daresbury, Glasgow, Liverpool, Imperial College, Oxford, RAL, QMUL, Sheffield

High Power RF Faraday Partnership

K. Long, 11 April 2023

Neutrino Factory: physics case Neutrino oscillations – established exptly

Implications for particle physics: Neutrino mass > 0 CP violation in the lepton sector?

Impact on astrophysics and cosmology: Origin of matter (leptogenesis) Dark matter

Require dedicated exptl programme to: Search for leptonic-CP violation Precisely measure parameters

Neutrino Factory: concept

NF: UK contributions to date- Proton driver:Schemes for:

RAL: NF and ISIS upgrades based on RCS

CERN: RCS in ISR tunnel

Contribution to SPL

Fermilab: Contribution to design of 8 GeV booster

J-PARC: Contribution to 3 GeV proton ring

NF: UK contributions to date5 MW proton driver developed from ISIS synchrotron

NF: UK contributions to date- Proton driver:

CERN:

30 GeV rapid cycling synchrotron in the ISR tunnel

NF: UK contributions to date- Targetry: Target system:

Power dissipation and thermal shock:

Rotating solid band (see R. Bennett)

Particle production and capture

HARP: Target assembly

Software

Leadership in analysis

Data taking complete

NF: UK contributions to date- Muon front end: Ionisation cooling:

Principle::

MuScat:Measure MCSdistributions

Practice:

MICE

Simulation: Ring coolers

Alternatives

Data taking complete

NF: UK contributions to date- international Muon Ionisation Cooling Expt:

142 authors, 37 institutes, 3 continents!

NF: UK contributions to date- MICE

The vision: neutrino physics

Prepare for era of precision neutrino physics

Worldwide consensus:

Neutrino Factory physics programme is:

Of fundamental importance

Complementary to that of LHC and LC

Neutrino Factory is the tool of choice

Therefore likely that it will be built. So:

The vision: UKNF proposal 2003 Programme of accelerator R&D that will:

Give the UK ownership of the key technologies: Proton driver front end Targetry Ionisation cooling

Conceptual design of complete facility: Embed results of hardware R&D Optimise entire complex

This will position UK to : Position UK to play lead role Possibly also to bid to host the facility

UK Neutrino Factory R&D activity

UKNF

MICE-UKWP1Conceptual

design

WP2Proton driver

front end

WP3Target studies

WP4Neutrino Factory design studies

D. FindlayR. Bennett

R. Edgecock

UK Neutrino Factory R&D activity

0

2000

4000

6000

8000

10000

12000

14000

1 2 3 4 5 6

Years (from 2004)

An

nu

al C

ost

(£k

)

WP3-TS

WP4

WP3 (ex TS)

WP2

WP1

Present request

04/05 05/06 06/07 07/08 09/09 09/100

2000

4000

6000

8000

10000

12000

14000

1 2 3 4 5 6

Years (from 2004)

An

nu

al C

ost

(£k

)

WP3-TS

WP4

WP3 (ex TS)

WP2

WP1

Present request

04/05 05/06 06/07 07/08 09/09 09/10

Front end test stand — WP2

Work package manager:David FindlayAccelerator DivisionISIS DepartmentRutherford Appleton Laboratory

Michael Clarke-GaytherAlan LetchfordJohn Thomason

Why interest in front end?

Front end of machine is where

currents and duty cycles are set for whole machine

beam quality is set for whole machine

UKNF: 4 MW — Front end must be good!

Multi-megawatt proton accelerators are new

Neutrino factories

Neutron sources, transmutation,tritium, energy, etc.

1 W/m loss max., ~10—7 loss per metre

Strong overlap

Neutrino factory proton driver:

Ion source (65 mA)

LEBT (low energy beam transport)

RFQ (75 keV 2.5 MeV, 280 MHz)

Chopper (typically ~30% chopped out)

DTL (2.5 MeV 180 MeV, 280 MHz)

Achromat

Synchrotrons

Front end must be good, so need a front end test stand to make sure!

Front end

Ion source: H—, 65 mA, 400 µs

2 × 2 × world’s leading H— source — ISIS

Existing negative ion source development programme at RAL for HPPAs in general

ASTeC

EU (network HPRI-CT-2001-50021)

This ion source programme a benefit to UKNF front end test stand programme

Ion Source Development Rig at RAL

LEBT and RFQ

Low energy beam transport

Matches 65 mA from ion source to RFQ

RFQ

4-rod, 75 keV 2.5 MeV, 280 MHz

These less of a problem

Can base on experience of LEBT and RFQ for ISIS and outline designs for ESS

More a matter of implementation than R&D

But ~1–2 MW RF driver required for RFQ

UKNF RFQ will be ×3 longer and in square section vessel

Beam loss

Why chopper?

Ion source Linac Ring

Bunching

Also to minimise RF transients and control beam intensity

>10 × ISIS

No beam loss

Ion source Linac Ring

Bunching

With chopper — gaps in beam

Good

Bad

Chopper performance required

DC accelerator

RF accelerator

ns – µs spacing

UKNF: 280 MHz, bunch spacing 3.57 ns

On

Off

Switch between bunches

Partially chopped bunches a problem! Tune shifts!

Choppers across the world:

SNS 402 MHz, slow — only chopper built

CERN 352 MHz, SPL — work proceeding

RAL 280 MHz, fast, rugged, “UK”

SNS, 2½ ns per bunch

LEBT MEBT

RAL aspiration:switch in 2 ns and dissipate ~3–4 kW when “off”

2-stage processSlow transmission line

Lumped line — thermally hardened

0

1

0

12 ns 8

ns

RAL beam chopper— outline scheme

Need to build andtest with bunched beam

Beam

~1 m

Buncher cavity

Fast switch

Slow switch

Buncher cavity

Ion source (R&D already

under way)

LEBT

RFQ (bunches beam)

Chopper

Diagnostics

Experience of building test stands at RAL — ISIS RFQ test stand

Build test stand

Front end test stand at RAL — 3 and 6 year costs

SY £k (hardware incl. VAT + contingency)

Overall design + infrastr. 8 8 398 398

Ion source 6 7 324 347

LEBT 2 5 139 231

RFQ 1 14 46 1388

Chopper 14 48 623 1990

1530 4355 hardware

65 185 travel

30 82 1631 4495 staff

3226 9035 total

Front end test stand at RAL — time scales

Outline design Expect to build in R8 at RAL

Specifications Including monitoring/control specifications

Install infrastructure Electricity, air, water, (lead) shielding, initial monitoring/controls

Procure & install mechanical support structures HV platforms, LEBT + RFQ + chopper supports, etc.

Develop, procure & install ion source Source, vac., HV sys., arc & extract drivers, monitoring/control

Design, procure & install LEBT (incl. diagnostics) 3-solenoid LEBT incl. emittance scanners

Design, procure & install RF driver for RFQ 1½ MW likely to be required

Design, procure & install RFQ 2–3 MeV, 4-rod, based on existing ESS design

Chopper: design & test off-line Slow & fast deflection systems without beam

Chopper: design complete system Incl. quadrupoles & RF buncher cavities

Design, procure & install beam diagnostics (at output of chopper) Long. & trans. emittances

Chopper: procure & install

Run complete test facility

2009–10 2010–11 2011–122005–06 2006–07 2007–08 2008–092004–05

Year 5 Year 6 Year 7 Year 8Year 1 Year 2 Year 3 Year 4

Front end test stand at RAL

Six-year programme to build

Costed on basis of test stand already built and working

~£4½M equipment

~80 staff-years

RAL + university staff

Physics and engineering of real accelerator facility

Proposal for a programme of Neutrino Factory research and development

WP-3 The Target

The Neutrino Factory Target

Work Package Manager - J R J Bennett

CCLRC, RAL

Schematic diagram of the target and collector area

proton beam 4 MWtarget 1 MW

beam dump

pion collector solenoids

to the muon front-end

3 MW

s/s

thick shield walls

ParametersProton Beam pulsed 10-50 Hz pulse length 1-2 s energy 2-30 GeV average power ~4 MW Target (not a stopping target)

mean power dissipation 1 MW energy dissipated/pulse 20 kJ (50 Hz) energy density 0.3 kJ/cm3 (50 Hz)

2 cm

20 cm

beam

Target Developments – so far

1. Mercury Jets (USA and CERN)

2. Contained Flowing Mercury

3. Granulated Targets (CERN)

4. Solid targets (USA and RAL)

5. Solid Rotating Ring (USA and RAL)

• The mercury jets have had most development

• All schemes have advantages and disadvantages

The RAL scheme

Large rotating toroid cooled by

Thermal Radiation

This is very effective at high temperatures due to the T4 relationship (Stefans law).

40

41 TTAW

Schematic diagram of the radiation cooled rotating toroidal target

rotating toroid

proton beam

solenoid magnet

toroid at 2300 K radiates heat to water-cooled surroundings

toroid magnetically levitated and driven by linear motors

POWER DISSIPATION

0.01 0.1 1 10 100 1 103

0.01

0.1

1

10

100

1 103

power

MW10 m

10 m

v = 100 m/s

1 m

1 m

100 m

100 m

0.1 m

200 m

20 m10 m

2 m

0.1 m

1 m

2000 m

1000 m

radius/velocity

v = 20 m/s

v = 10 m/s

v = 1 m/s

v = 0.1 m/s

1000 m

10 m

100 m

10000 m5m radius

10 m/s velocity

Thermal Shock

Simple explanation of shock waves

inertia prevents the target from

expanding until:

the target expands by Δd

(axially)

target

the temperature rises by ΔT

Short pulse of protons

short pulse of protons

Time

t = 0

2d

t > 0

v is the velocity of sound in the target material.

Δd

v

dt

compression

tensio

nvelocity V

Shock, Pulse Length and Target Size

If a target is heated uniformly and slowly – there is no shock!

Or,

when the pulse length t is long compared to the time taken for the wave to travel across the target – no shock effect!

So,

if we make the target small compared to the pulse length there is no shock problem.

For the case of the neutrino factory target:

Assume t = 2 s, V = 3.3x105 cm s-1 , then d = 0.7 cm

Energy density is the key parameter

Table comparing some high power density pulsed targets

Facility Particle Target material

Energy density per pulse

J cm-3

Life,

no. of pulses

NuFact p Ta 318 109

(7x106 for the toroid)

ISOLDE

(CERN)

p Ta 279 2x106

Pbar (FNAL)

p Ni 7112 5x106

Damage

NuMI p C 600 Shock not a problem

SLC (SLAC)

e W26Re 591 6x105

RAL/TWI e Ta

thin foil

500 106

Proposed R&D1.Calculate the energy deposition, radio-activity for

the target, solenoid magnet and beam dump. Calculate the pion production (using results from HARP experiment)

and calculate trajectories through the solenoid magnet.

2. Model the shock a) Measure properties of tantalum at 2300 K b) Model using hydrocodes developed for explosive applications at LANL, LLNL, AWE

etc. c) Model using dynamic codes developed by ANSYS

Proposed R&D, continued

3. Radiation cooled rotating toroida) Calculate levitation drive and stabilisation systemb) Build a model of the levitation system

4. Individual bars a) Calculate mechanics of the system b) Model system

5. Continue electron beam tests on thin foils, improving the vacuum

6. In-beam test at ISOLDE - 106 pulses

7. In-beam tests at ISIS – 109 pulses

8. Design target station

solenoid

collection and cooling reservoir

proton beam

Levitated target bars are projected through the solenoid and guided to and from the holding reservoir where they are allowed to cool.

Equipment and Staff Costs over the first 3 years (excluding VAT)

Item Staff Years Cost, k£

1. Management 1 30

2. Target and Target Station Design 1 10

3. Nuclear Studies 8.9 30

4. Shock Studies 4.6

Measurements 280

Modeling 30

5. Electron Beam Tests 1

Improvements (mainly vacuum) 100

Tests 10

6. Tests at ISOLDE 1

Target 30

7. Levitation Studies 6

Theoretical studies 10

Model tests 100

VAT 110

Travel 45

Total 23.5 (£961k) 785

Year

ITEM 1 2 3 4 5 6

1. Management

2. Target Station Design

3. Nuclear Studies

4. Shock Studies

5. Electron Beam Tests

6. Tests at ISOLDE

7. Levitation Studies Individual bar studies

8. Build target station at ISIS Life Test

Decision on solid target

Time scale

Proton beam

Mercury jet Solenoid

Effective target length ~20 cm

Schematic diagram of the mercury jet target

To mercury pump & heat exchanger

Protons

Tube containing flowing mercury

20 T solenoid magnet

Schematic diagram of the contained flowing mercury target

Solid bar targetNeed to dissipate the heat:

a) water cooling difficult – “dilutes” target

b) radiation cooling not possible

c) need moving target – multiple targets

drive shaft

protons

spoke

solenoid coils

vacuum box

target

Rotating wheel target

1MW Target Dissipation (4 MW proton beam)

tantalum or carbon radiation cooled temperature rise 100 K speed 5.5 m/s (50 Hz) diameter 11 m

Plan View of Rotating Band Target (Bruce King et al)

shielding

rollersAccess

port

rollers

rollers

protonsto dump

cooling

coolingcooling

solenoid channel

1 m water pipes

x

z

Table comparing some high power pulsed proton targetsFacility Particle Rep. Power Energy Energy Life Number

Rate /pulse density of pulses/pulse

f P Q height width length volume thick material q N

Hz W J cm cm cm cm3 cm J cm-3 days

NuFact protons 50 1E+06 20000 2 2 20 63 20 Ta 318 279 1.E+09Number of pulses on any one section of the toroid 7.E+06

ISOLDE protons 1 3675 0.6 1.4 20 13 0.05 to Ta 279 21 2.E+060.0002

ISIS protons 50 180000 3600 7 7 30 1155 0.7 Ta 3 450 2.E+09

Pbar protons 0.3 1797 0.19 0.19 7 0.25 ~6 Ni 7112 186 5.E+06 Run I 3E12 ppp (Cu, SS, Inconel) Damage

Run II 5.E+12 Damage in one or a few pulses 13335

Future 1.E+13 0.15 0.15 30000

NuMI protons 0.53 0.1 0.1 95 2 C 600

120 GeV Radiation Damage - No visible damage at 2.3E20 p/cm2

4E13 ppp Shock - no problem up to 0.4 MW (4E13 at 1 Hz)8.6 s Sublimation -OK

Reactor tests show disintegration of graphite at 2E22 n/cm2

NuMI will receive a max of 5E21 p/cm2/year

Beam and Target size

Facility Particle Rep. Power Energy Energy Life Number Rate /pulse density of pulses

/pulsef P Q height width length volume thick material q N

Hz W J cm cm cm cm3 cm J cm-3 days

NuFact protons 50 1E+06 20000 2 2 20 63 20 Ta 318 279 1.E+09Number of pulses on any one section of the toroid 7.E+06

SLC e 120 5.E+03 42 0.08 0.08 2 W/Re 591 1500 6.E+05SLAC 33 GeV Rotating disc, 6.35 cm diameter, 2cm thick 26% Re

Target designed to withstand shock

Radiation damage leading to loss of strength and failure when subjected to shock

FXR e Ta 160 100LLNL 17 MeV Ta 267 10

No damage

RAL/TWI e 100 4.E+04 0.2 25 m Ta 500 up to 1E+06150 keV Thin foil 0.4 cm wide Range ~10 m

Failures probably due to oxidation in poor vacuum

Beam and Target size

Table comparing some high power pulsed electron targets