Update on MOMENT’s Target Station Studies Nikos Vassilopoulos, IHEP/CAS Hanjie Cai, IMP/CAS

Nikos-MOMENT Target Studies Layout MOMENT in future Leptonic CP-violation Decay at rest source Pions decays neutrino beam Description Why a MW system Application Hg liquid jet pion capture Radiation Future: Granular Waterfall Comparison with Hg-jet R&D project NuFact17-Sep 2017 Nikos-MOMENT Target Studies

MOMENT’s high-field superconducting solenoid Baseline design: super conductive solenoid from ~ 14 T -> 3 T 2 first Nb3Sn coils, 3 last NbTi coils 80 -> 60 cm thick W-shielding <-> 15 MW proton beam NuFact17-Sep 2017 Nikos-MOMENT Target Studies

MOMENT’s high-field superconducting solenoid ~ 1 m aperture due to collection of secondary /tertiary beams and space for inner shielding Based on Nb3Sn superconducting conductors, CICC (Cable-in-Conduit Conductor) coil (ITER) HTS coils are also under consideration High-field magnet R&D efforts at IHEP (incorporated with SPPC) NuFact17-Sep 2017 Nikos-MOMENT Target Studies

π+ production and PT acceptance for adiabatic solenoids for any adiabatic taper solenoid B1=14 T, r1 = 20 cm PT1 = 420 MeV/c B2 = 3 T, r2 = 43 cm PT2 = 193 MeV/c _ π+ for <Eμ> ~ 300 ± 50% MeV (<Eμ> ~ 57 % <Eπ> ) PT accepted r1 = 20 cm, r2 = 43 cm PT accepted r1 = 14 cm, r2 = 30 cm PT accepted r1 = 7 cm, r2 = 15 cm capture PTmax = 3 * Bz (T) * rcs (cm) / 2 _ FLUKA 2015 (1e6 p.o.t.) NuFact17-Sep 2017

Target for neutrinos and muons Hg-jet target (similar to NF design, MERIT) as baseline Higher beam power: heat load, radioactivity <-> 15 MW On the other hand, easier to some extent due to CW proton beam (no shock-wave problem) More interests in developing fluidized granular target in collaborating with C-ADS target team (why, explained later) MERIT (2007), Hg-jet & p-24 GeV @ 5, 10, 15 T: MERIT: Proof-of-principle for generating intense muon and neutrino beams from liquid Hg-jet and protons NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies Target evolution from conventional neutrino beams to super beams, MOMENT, neutrino factories & muon collider Chris Densham or segmented flowing types (liquids, granules…): heat transfer: dissipate high energy densities, high total power can be pumped away, cooled externally & recirculated, material replenish CNGS (segmented), T2K, T2HK, nuSTORM, NOvA, LBNF/DUNE… Super Beams: SPL, ESSnuSB NF (?) MOMENT, NF, Muon Collider… NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Optimization of pion capture adiabatic field analysis: slower vs fast tapers Hg-jet target: tilt, length, radii, proton beam size proton beam energy W-waterfall granular target comparisons between different Monte – Carlos (FLUKA-GEANT4) NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Adiabatic field analysis: slower vs fast tapers, why does it matter ? For an adiabatic reduced field coil shield aperture limits maximum transverse momentum at target region transverse momentum reduction along taper meson beam size expansion <-> shield configuration at MCS slower taper <-> thicker shielding pion capture PTmax = 3 * Bz (T) * rcs (cm) / 2 B2<B1 Adiabatic, slow field change, conservation of magnetic flux B1 helical trajectories B x r2 = C -> r2/r1 = √B1/B2 P2T / B = C -> PT2/PT1 = √B2/B1 NuFact17-Sep 2017 Nikos-MOMENT Target Studies

adiabatic field analysis slower decrease, thicker shielding steepest decrease, baseline L = 5 m NuFact17-Sep 2017 Nikos-MOMENT Target Studies

particle yields for Ltaper= 5 m as function of proton Ek + 2.5 GeV π+μ 2 GeV 1.5 GeV selection in red pions 0.222 < P (GeV/c) < 0.776 muons 0.111 < P (GeV/c) < 0.438 statistical error < 1 % tilt 2.5 GeV 2.5 GeV π+μ π+μ 2 GeV 2 GeV 1.5 GeV 1.5 GeV length radii NuFact17-Sep 2017 Nikos-MOMENT Target Studies

particle yields for Ltaper= 50 m as function of proton Ek + 2.5 GeV μ 2 GeV 1.5 GeV selection in red pions 0.222 < P (GeV/c) < 0.776 muons 0.111 < P (GeV/c) < 0.438 statistical error < 1 % tilt 2.5 GeV 2.5 GeV μ μ 2 GeV 2 GeV 1.5 GeV 1.5 GeV length radii NuFact17-Sep 2017 Nikos-MOMENT Target Studies

yields as function of tilts at 2 GeV for π+, π- & μ+, μ- Ltaper = 5 m π+ π- Ltaper = 50 m μ+ ~75 % μ- selection in red pions 0.222 < P (GeV/c) < 0.776 muons 0.111 < P (GeV/c) < 0.438 statistical error < 1 % ~ 90 % NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Hg-jet optimized parameters FLUKA, 5, 50 m inverse Gaussian + 1st degree inverse adiabatic solenoid: tilt 100 mrad or more length 25 cm or more radius 5 mm or more Geant4beamline: 10% less yieds similar values of target physical parameters NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Radiation studies: energy deposition energy deposition on coils and shield with FLUKA deposited energy caused by charged particles, gammas, neutrons total energy : 10 MW max. volumetric heat : 100 W/cm3 energy deposition in SC below 1 kW He or water cooling multiple channel is studied for the shield NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Radiation damage: neutron flux & dpa neutron flux per year as function of radius, length CS dpa per year as function of radius, length CS FLUKA Radiation damage: neutron flux > 1021 n / m2 / year Damage Al or Cu-stabilizers of Nb3Sn and NbTi superconductor wire Loss of electrical and thermal conductivity of the stabilizers and the whole coil respectively Al-stabilizer could recover 100% by annealing dpa > 1 per year shield deterioration in the region surrounding the Hg-jet Future shield optimization with slower adiabatic taper and verification with other monte-carlos NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Granular waterfall as alternative flowing target @ 15 MW Why using an alternative flowing target other than Hg-jet toxicity -> recirculation circuit possible technical limitations with jet velocity: needs 70 m/s to accommodate 15 MW -> questionable jet stability high number of neutrons -> radiation damage on shield and coils (high Z) Neutrino Factory and Muon Collider studies (US) considered Gr target for up to 1.5 MW (from 2000, nuFact15-16) What are the advantages of a granular waterfall target over a liquid one high flow rate, large stream cross section -> high power densities absorbed and removed reliable, circuit simplicity -> gravity driven flow of granules material is already broken – intrinsically damage proof no cavitation, splashing or jets as for liquids shock waves constrained within material grains If the new target produces similar meson yields then is considerable. Are the reduced and variable (effective) density and the geometry of the waterfall an obstacle to pion’s generation ? NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Waterfall granular target project for MOMENT Discrete Element Model MC at IMP, ADS & MOMENT target groups (NuFact16, “Phys.Rev.Accel.Beams 20 (2017) no.2, 023401”) Toy FLUKA model (2015, NuFact16) shows -10 % captured pions all momenta in black selection in red 0.22 < P (GeV/c) < 0.78 statistical error < 1 % Hg-jet 0.077 π/p.o.t. 0.063 π/p.o.t. toy W-waterfall model indicates that pion yields not restrained by the reduced density and geometry of the waterfall DEM analysis indicates that the right flow rate and velocity can be achieved but effective density is not optimized in this study granular waterfall target has the potential to be considered alternatively NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies Schematic of the granular waterfall target station NuFact17-Sep 2017 Nikos-MOMENT Target Studies

representation in FLUKA, 100 mrad turn, 5 m taper, W-slab with reduced density x downstream x z y y upstream z x NV @ nuFACT17 MOMENT

best π-yields for W-waterfall as function of density Hg 0.077 π/p.o.t. 0.063 π/p.o.t. λW(100%) = 10 cm all momenta in black selection in red pions 0.222 < P (GeV/c) < 0.776 statistical error < 1 % NV @ nuFACT17 MOMENT

π-yields as function of L, dW = 56 % 100 mrad turn π+/π- = 1.86/1. 10% less pion yield than Hg-jet target Hg 0.077 π/p.o.t. 0.063 π/p.o.t. λW = 10 cm NV @ nuFACT17 MOMENT

Schematic representation of beam-target interaction for the granular waterfall target Density distributions with different width with DEM analysis Density distributions

Nikos-MOMENT Target Studies Different regions for the liquid mercury/powdery tungsten jet and the granular waterfall Parameters of the beam profile and the target geometry varies ~ 2.5 m/s Dominant advantage of granular waterfall: Larger mass flow for heat removing than others NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Tunnel Geometry: Magnetic Field: D0.6 x L50 m Magnetic Field: 15T in beam-target interaction region, tapers to 4T when z > 15 m Muon yields collected at z=50 m for different target widths and lengths: P (GeV/c) > 0 150 < P (GeV/c) < 450

Nikos-MOMENT Target Studies Comparison to Hg Jet Produced Pions Collected Muons Pi+ Pi- P (GeV/c) > 0 150 < P (GeV/c) < 450 Hg Jet Granular Waterfall Muon yield: ~20% less Averaged energy: higher very close NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Future joint-project with C-ADS working group It will be proposed to NSFC, IHEP & IMP, March 2018): Simulations in order to realistically achieve similar capture efficiency with Hg-jet and efficient heat transfer Geometry effective density flow rate and velocity Experiment verification of reliability and stability of the waterfall flow interaction with high magnetic field test different materials Aim to answer about its feasibility NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies conclusions In the case of Hg-jet: physical parameters as tilt angle, radius, length optimized further shielding optimization feedback from EMuS studies on neutron radiation Important to proceed with R&D for the granular waterfall: only 20% less yields than Hg-liquid jet using DEM analysis parameters simulations for further physical parameters optimizations and experiment for validation, IHEP and C-ADS target group/IMP target solution of multi-MW neutrino and muon beams Thanks NuFact17-Sep 2017 Nikos-MOMENT Target Studies

inversed 1st degree polynomial field: field approximation implemented in FLUKA: L = 5, 10, 15, 20, 50 m The question is what do we prefer muons or pions 5 m

Waterfall granular target for MOMENT - I granular waterfall L = 5 m, 5 - SC coils rm = 20 cm to 40 cm 14 T to 3 T Hg-jet might not be applicable for high power targetry in neutrino beams High toxicity (Hg-pool) , severe radiation damage on the shields due to high Z (Chin.Phys. C40 (2016) no.12, 126001), also jet kinematic limits due to interaction with 14 T Topic studied and presented at NuFact15-16 workshops, also studied in International Neutrino Factory Tungsten waterfall granular target Fluidized <-> heat removal/exchange -> recyclable, less radiation (smaller Z) Preliminary studies on the waterfall parameters and radiation with FLUKA and Discrete Element Methods MCs (NuFact16 workshop, “Phys.Rev.Accel.Beams 20 (2017) no.2, 023401”), on-going NuFact17-Sep 2017 Nikos-MOMENT Target Studies

simulation representation (in FLUKA) figure of merit: π, μ, p yields, distributions downstream of: the Main Capture Solenoid (MSC) Adiabatic Transport Solenoid Main Capture Solenoid “idealized” field B = 14 T, LMCS= 32 cm, rMCS= 20 cm study tilts, lengths, radii, beam-sizes Gaussian field approximation at MCS MSC Bz= 14 T -> 3 T ----->--->-->-> Adiabatic Transport Solenoid L = 5, 10, 15, 20, 35, 50 m r = 20 cm - > 43.2 cm B = 14 T -> 3 T Bz= 14 T --->--->---> NuFact17-Sep 2017 Nikos-MOMENT Target Studies

MOMENT - Target Station: G4 vs FLUKA Zhao Guang, IHEP/ CAS similar shape, slightly different scale NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies Granular waterfall in the strong magnetic field The grains would be charged by proton, the deflecting force, however, would be small enough. mass flow rate: 62.2 kg/s charging rate: 10 mA/s electric quality: ~1.6E-4 C/kg velocity: ~ 3 m/s magnetic: 15 T deflecting force: ~ 7.2E-3 N/kg Usually, the equivalent grounding resistance is finite, Thus, this force should be much smaller. Low electric conductivity and magnetic susceptibility to avoid shape transformations and instabilities of the waterfall. Tungsten carbide: Magnetic susceptibility (~ +5.0E-9, ~ 1.7E-4 times that for Hg). Electric conductivity (< 400 S/m, ~ 4.0E-4 times that for Hg). NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Power deposit (8 GeV & 0.5mA) Cai Hanjie/ IMP, CAS A much smaller power deposited in unit mass of waterfall target

Nikos-MOMENT Target Studies NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Beam escaping The percent of the escaped beam (after main target) is quite large. The granular flow in the chute can act as second target and produce additional pions.

Nikos-MOMENT Target Studies NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Nikos-MOMENT Target Studies Recalculation of the neutrino fluxes with FLUKA, μ+ and μ- beams assuming 100% charge separation and channel transmission detector @ 150 km - νμ νμ μ+ νe μ- - νe detector @ 150 km μ+ μ- Ν ν (x1012) / m2 / 1024 p.o.t. <E> MeV Ν ν (x1011) νμ - 5.76 183 1.46 200 νe 1.42 193 5.84 175 - stat. error ~ 1.5% - NuFact17-Sep 2017 Nikos-MOMENT Target Studies

Why is this research important ? MOMENT -> Option after JUNO -> Neutrino Factory -> Ultimate future machine for accelerator produced neutrinos, a dream machine of many MOMENT Target Station <-> Muon Collider Target station -> Future option in collider physics 2017-6-8 NV- IHEP Report 2017