Target concepts for future high power proton beams

Target concepts for future high power proton beams A. Fabich CERN AB-ATB, Switzerland April 2005 A. Fabich, CERN 1

Outline n Demand for “human made” neutrino beams n n n A neutrino factory A high power proton driver Target station n n Secondary particle production Target concepts n Solid targets n Liquid targets n n Jet target Worldwide R&D CNGS graphite target assembly (2005, D. Grenier et al. ) April 2005 A. Fabich, CERN 2

Neutrino oscillations Observation: into another of different flavour Results: NEUTRINOS HAVE MASS STATES FLAVOUR STATES 6 Parameters: n Three mixing angles n Two Dm 2 differences n 3 masses n One delta phase (CP-violation angle) Transition probability: April 2005 A. Fabich, CERN 3

Neutrino parameters to measure n n n Measure 13 via P( e m) with a precision of 10 -3 or setting a limit to 10 -6 Determine the sign of Dm 223 Discover and measure the CP violation in the leptonic sector P( e m) Need of high energy e: m+ e+ m April 2005 A. Fabich, CERN 4

neutrino beams/experiments “Human made” neutrino beams provide advantage of n pure neutrino flavour n with known parameters (E, intensity, direction, …) n Switching the helicity by switching the parental sign n A stage towards a muon collider … Future installation (constructed or considered) n to look for 13 n Look for e in beam (CNGS, ICARUS, MINOS) n Off-axis beam (JHF-SK, off axis NUMI) n Low energy Super. Beam n to look for CP/T violation or for 13 (if too small) n Beta-beams (combined with Super. Beam) n n April 2005 Beta-beam: neutrinos from beta-decay of boosted isotopes Neutrino Factory: high energy e oscillation A. Fabich, CERN 5

Proposal for a CERN - Super Beam Far detector + + + e Background + e++ + e April 2005 A. Fabich, CERN 6

1016 p/s m+ e++ m + e 0. 9 1021 m/yr m m + m m- 3 1020 e/yr 3 1020 m/yr April 2005 Oscillation Wrong Sign muons A. Fabich, CERN 7

High Power Proton Beam -factory: p + p +, K + + … 2 nd generation + + + 3 rd generation + e + + + e 4 th generation flux of 1021 neutrinos/year requested by physics high power primary proton beam (average 4 MW) required with losses assumed in production chain new challenge - not only for proton driver e. g. BNL/AGS, CERN/SPL - esp. for production targets April 2005 A. Fabich, CERN 8

“Secondary” particle generation n Produce unstable daughter particles of interest: n n Neutrons, radio-isotopes, pions, kaons, muons, neutrinos, … with highest flux possible achieve high statistics and/or background suppression n Collider luminosity: L = N 2 f / A n sometimes (e. g. neutrino factory) the particle flux is relevant only, beam size A is not of high importance n Primary proton beam strikes target n n April 2005 Today typical proton beam power: average 10 to 100 k. W Target materials: mainly solids from beryllium to lead A. Fabich, CERN 9

Target failure n n Increasing proton beam power without paying attention leads to uncontrolled energy deposition Causes excessive heating structural failure Above 20 % of the primary beam power are deposited in the target! April 2005 A. Fabich, CERN No quotation on purpose 10

Hot issues for a target induced by the proton beam n Thermal management (heat removal) n n n Radiation damage n n Target melting Target vaporization change of material properties Thermal shock n April 2005 Beam-induced pressure waves A. Fabich, CERN 11

Future target stations Neutrino Facilities Isotope production JPARC Superbeam Neutrino factory Muon collider Beta beam RIA EURISOL Spallation Sources ESS LANSCE MEGAPIE SNS Target Development Antiproton Source Pbar Hadron Beam Facility Materials Irradiation Facilities JPARC IFMIF LEDA LANSCE April 2005 A. Fabich, CERN 12

Solid targets Numerous applications today: but proton beam power < 100 k. W n Common materials: Beryllium, carbon, tantalum, … n n low coefficient of thermal expansion High melting point High production yield … Studies n BNL for a 1 MW proton beam (average) n ISOLDE with a 10 k. W -”n CNGS with a 700 k. W -”n … April 2005 A. Fabich, CERN 13

Pion yield optimisation n n fixed proton energy (2. 2 Ge. V) as a function of the target material S. Gilardoni capture losses not included in figure April 2005 A. Fabich, CERN 14

The Harp experiment Hadron production cross section measurement April 2005 A. Fabich, CERN 15

Towards 1 MW on target n CNGS: CERN neutrinos to Gran Sasso, start 2006 750 km neutrino beam line 0. 75 MW proton beam power n Target: graphite n n n 10 x rods n n n high pion production small good tensile strength l=10 cm, d=5 mm Helium cooled CNGS graphite target assembly (2005, D. Grenier et al. ) Major concerns for target failure in case of abnormal operation of not centered beam April 2005 A. Fabich, CERN 16

Carbon an ultimate candidate? Very good material properties like thermal expansion, but … n For Carbon 2 I = 80 cm target not point-like n n n difficult to find an efficient horn design cost of the solenoid capture Pion time spread too large for subsequent phase rotation n Carbon would add > 0. 5 nsec Pion time spread April 2005 A. Fabich, CERN 17

Limit of carbon target lifetime K. T. Mc. Donald n A Carbon target in vacuum sublimates away in one day at 4 MW. n In an helium atmosphere: sublimation negligible? Radiation damage limits lifetime to about 12 weeks n April 2005 A. Fabich, CERN 18

Rotating toroidal target rotating toroid 4 m/s toroid (d=6 m) magnetically levitated and driven by linear motors R. Be nnet t, B. K ing e t al. • Distribute the energy deposition over a larger volume • Similar a rotating anode of a X-ray tube toroid at 2300 K radiates heat to water-cooled surroundings solenoid magnet proton beam n. Tensile strength of many metals is reached with stresses induced by the equivalent of a 1. 5 MW proton beam structural failure April 2005 A. Fabich, CERN 19

Target material studies n n n CTA Tensile strength … Studies ongoing at BNL April 2005 A. Fabich, CERN H. Kirk, N. Simos et al. Radiation induced change of material properties: 20

Granular target n n April 2005 Volume of Tabtalum beads, d~2 mm Cooled by liquid or gas A. Fabich, CERN 21

Granular target P. Sievers et al. n Tantalum Spheres: = 2 mm, n Small static thermal stress: Each sphere heated uniformly. n Small thermal shock waves: Resonance period of a sphere is small relative to the heating time n Large Surface / Volume: Heat removed where deposited. n Radiation/structural damage of spheres, container and windows: n Lifetime of Target > Horn to be expected ? n R&D not pursued April 2005 A. Fabich, CERN = 0. 6 x 16. 8 10 g / cm 3 22

Contained liquid target n SNS, ESS: high power spallation neutron sources n n 1 m/s mercury flow Liquid immune to stresses passive heat removal No water cooling n Not an option for charged particles n n !!! Beam window: n Beam induced stresses n Cavitation induced erosion (pitting) April 2005 A. Fabich, CERN T. Gabriel et al. 23

Cavitation induced erosion (pitting) Before Containment failure After 100 pulses at 2. 5 MW equivalent intensity “solved by”: n surface treatment n Bubble injection April 2005 A. Fabich, CERN 24

4 MW Proton driver BNL CERN 24 2. 2 3 1013 24 1013 Rep. rate [Hz] 32 50 Pulse length [ns] 5 3200 Focusing element 20 T solenoid Magnetic horn Energy [Ge. V] Proton intensity/pulse April 2005 A. Fabich, CERN 25

Magnetic Horn Magnetic volume according to the Ampere law: B=0 r B Current OUT Current IN April 2005 A. Fabich, CERN 26

First piece of Nufact B Merci à l’ atelier du CERN April 2005 A. Fabich, CERN 27

US-Nu. Fact: 20 T Solenoid • Focusing: Tapered field 20 T 1. 25 T • Magnetic flux conservation Capture B=20 T F = 15 cm, L=30 cm April 2005 B(T) • Angular momentum conservation A. Fabich, CERN cm 28

Focusing options Increase secondary acceptance n Magnetic Horn (CERN) n Solenoid (US) n B = 20 T at target Adiabatic focusing channel Two charges collected can be separated by RF p Protons B 1/R target Current 300 k. A n n n B=0 T at target Focuses only one charge state, which is required for super-beam highly restricted space April 2005 n n A. Fabich, CERN 29

Liquid target with free surface n n n jet avoid beam window v~20 m/s Replace target at 50 Hz each proton pulse sees new target volume Cooling passively by removing liquid n no water-radiolysis ? ? ? What is the impact on the jet by • 4 MW proton beam • 20 T solenoidal field April 2005 A. Fabich, CERN 30

Target properties n Ep>10 Ge. V: high Z n n point-like source L = 2 nuclear interaction length R= 5 mm Tilt: 100 (150) mrad n April 2005 Limited by bore A. Fabich, CERN 31

Mercury n Advantages n n High Z Liquid at ambient temperature n n n Easily available Disadvantages n n Toxic “only” compatible with very few materials n n April 2005 Highly convenient for R&D Stainless steel, Titanium, EPDM, … High thermal expansion coefficient A. Fabich, CERN 32

Proton induced shock(s) n n Proton intensity: 3 1013(14) p+/pulse d. E/dx causes “instantaneously” d. T of Gaussian shape within pulse duration pressure gradient accelerates … d. P/dr=-dv/dt vdipersal~ d. E/dm 1/cp vsound vdipersal~50 m/s for d. E/dm=100 J/g April 2005 A. Fabich, CERN 33

Hg Jet test a BNL E-951 Protons P-bunch: Hg- jet : April 2005 2. 7 1012 ppb 100 ns to = ~ 0. 45 ms diameter 1. 2 cm jet-velocity 2. 5 m/s perp. velocity ~ 5 m/s A. Fabich, CERN 34

Proton beam on mercury Jet Recorded at 4 k. Hz Replay at 20 Hz BNL AGS Proton beam 1 cm April 2005 Hg jet v=2 m/s A. Fabich, CERN 35

Proton beam on mercury Jet Recorded at 4 k. Hz Replay at 20 Hz BNL AGS Proton beam 1 cm Hg jet v=2 m/s Splash velocity max. 50 m/s April 2005 A. Fabich, CERN 36

Proton beam on mercury Jet BNL AGS Proton beam 1 cm April 2005 Hg jet v=2 m/s A. Fabich, CERN 37

Proton beam on mercury Jet BNL AGS Proton beam 1 cm Hg jet v=2 m/s Splash velocity max. 50 m/s April 2005 A. Fabich, CERN 38

Experimental results n n n Scaling laws for splash velocity in order to extrapolate to nominal case Beam variables: pulse intensity, spot size, pulse length, pulse structure, beam position Benchmark for simulation codes April 2005 A. Fabich, CERN 39

Simulation: Shocks Frontier code, R. Samulyak et al. Initial density Initial pressure is 16 Kbar Density at 20 microseconds 400 microseconds April 2005 A. Fabich, CERN 40

Magneto-hydro-dynamics (MHD) n 20 -T solenoid DC-field for sec. particle capture n Moving mercury target sees d. B/dt n Farady’s law eddy currents induced n Magnetic field acts back on current and mercury jet n Forces: repulsive, deflecting, quadrupole deformation, … April 2005 A. Fabich, CERN J. Gallardo et al. , PAC 01, p. 627 41

Previous experimental results 1 cm Dista nc e from nozzl e B=0 T 0 Tesla B=19. 3 T Jet smoothing 20 Tesla (damping of Rayleigh surface instability) nozzle 15 m/s mercury jet injected into 20 T field. April 2005 A. Fabich, CERN 42

MHD stabilization Simulation of the mercury jet – proton pulse interaction during 100 microseconds, B = 0 damping of the explosion induced by the proton beam April 2005 Frontier code, R. Samulyak et al. a) B = 0 b) B = 2 T c) B = 4 T d) B = 6 T e) B = 10 T A. Fabich, CERN 43

Experimental history ISOLDE GHMFL BNL TT 2 A Nu. Fact p+/pulse 3 1013 ---- 0. 4 1013 2. 5 1013 3 1013 B [T] --- 20 --- 15 20 Hg target static 15 m/s jet (d=4 mm) 2 m/s jet 20 m/s/ jet 20 m/s jet (d=10 mm) DONE 2007 DESIGN • proof-of-principle test proposed at TT 2 A @ CERN • Experimental setup: 15 T solenoid + Mercury Jet + proton beam • Completion of the target R&D for final design of the Hg-Jet April 2005 A. Fabich, CERN 44

Nominal mercury jet target test in TT 2 A at CERN n n Approved CERN experiment n. To. F 11 Setup: n Proton beam n n Proton beam 15 T solenoid 20 m/s mercury jet Collaboration: n n 24 Ge. V, nominal intensity BNL, ORNL, Princeton University, MIT, RAL, CERN, KEK Beam time in spring 2007 April 2005 A. Fabich, CERN 45

Conclusion n (Mercury) jet target a viable solution as a production target for a 4 MW proton beam and beyond! n Target R&D on target concepts different than jet are alive, but comparable small. n Synergies of target development for a large variety of applications. April 2005 A. Fabich, CERN 46