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, 01 September 2014

Neutrino Factory: physics case  Neutrino oscillations – established exp tly  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 expt l 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 date 5 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 MCS distributions  Practice:  MICE  Simulation:  Ring coolers  Alternatives Data taking complete

NF: UK contributions to date - international Muon Ionisation Cooling Exp t : 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-UKWP1 Conceptual design WP2 Proton driver front end WP3 Target studies WP4 Neutrino Factory design studies D. Findlay R. Bennett R. Edgecock

UK Neutrino Factory R&D activity Present request 04/05 05/06 06/07 07/08 09/09 09/10 Present request 04/05 05/06 06/07 07/08 09/09 09/10

Front end test stand — WP2 Work package manager: David Findlay Accelerator Division ISIS Department Rutherford Appleton Laboratory Michael Clarke-Gayther Alan Letchford John 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 ) 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 sourceLinacRing Bunching Also to minimise RF transients and control beam intensity >10 × ISIS

No beam loss Ion sourceLinacRing 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: SNS402 MHz, slow — only chopper built CERN352 MHz, SPL — work proceeding RAL280 MHz, fast, rugged, “UK” SNS, 2½ ns per bunch LEBTMEBT

RAL aspiration: switch in 2 ns and dissipate ~3–4 kW when “off” 2-stage process Slow transmission line Lumped line — thermally hardened ns 8 ns

RAL beam chopper — outline scheme Need to build and test 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 Ion source LEBT RFQ Chopper hardware travel staff total

Front end test stand at RAL — time scales

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 MW target 1 MW beam dump pion collector solenoids to the muon front-end 3 MW  s/  s thick shield walls

Parameters Proton Beam pulsed10-50 Hz pulse length1-2  s energy 2-30 GeV average power ~4 MW Target (not a stopping target) mean power dissipation1 MW energy dissipated/pulse20 kJ (50 Hz) energy density0.3 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 T 4 relationship (Stefans law).

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

5m 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 2d2d t > 0 v is the velocity of sound in the target material. ΔdΔd compression tension velocity 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 = 3.3x10 5 cm s -1, then d = 0.7 cm Energy density is the key parameter

Table comparing some high power density pulsed targets FacilityParticleTarget material Energy density per pulse J cm -3 Life, no. of pulses NuFactpTa (7x10 6 for the toroid) ISOLDE (CERN) pTa2792x10 6 Pbar (FNAL) pNi71125x10 6 Damage NuMIpC600Shock not a problem SLC (SLAC) eW26Re5916x10 5 RAL/TWIeTa thin foil

Proposed R&D 1.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 toroid a) Calculate levitation drive and stabilisation system b) 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 pulses 7. In-beam tests at ISIS – 10 9 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) ItemStaff YearsCost, k£ 1. Management Target and Target Station Design Nuclear Studies Shock Studies4.6 Measurements280 Modeling30 5. Electron Beam Tests1 Improvements (mainly vacuum)100 Tests10 6. Tests at ISOLDE1 Target30 7. Levitation Studies6 Theoretical studies10 Model tests100 VAT110 Travel45 Total23.5 (£961k)785

Year ITEM 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 target Need 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 rollers Access port rollers protons to dump cooling solenoid channel 1 m water pipes x z

Table comparing some high power pulsed proton targets

Table comparing some high power pulsed electron targets