Radioactive Ion Beam (RIB) Facility at VECC : - Saha Institute of ...

Radioactive Ion Beams : Ions of β-unstable nucleiUnknown territoryEnormous increase in the no. of available projectiles

Physics MotivationMaterial ScienceAdvantages of EMISSION CHANNELING technique :Req. implantation dose of radioactive atoms is significantly lower than thatof ion channeling experiment.‣Radiation damage during channeling analysis negligible.‣Sensitivity of EC >> higher than ion channeling tech. (1E13 & 1E18 /cc)

Physics Motivation • Material ScienceAdvantage of using RIB as a Mössbauer dopant are :‣Chemical incompatibility of Mössbauer atom is not an issue any more :possible to find a suitable compatible parent isotope which decays to theMössbauer atom.‣Site selective doping which depends on the parent isotopeFor example, 119 Sn – good Mössbauer dopant for group III-V compoundsemiconductors :119In 119 Sn (occupies group V lattice sites)119Sb 119 Sn (occupies group III lattice sites)

Physics MotivationMedical researchRadioisotope Therapy : A radionuclide is delivered to atumor site using a biologically active molecule whichdecays via β - or α.Using RIB one can produce such nuclide with high specificactivity as it will be carrier free or no-carrier-added form(suitable target+projectile & clean separation) + availabilityof new radioisotopes.PET (Positron Emission Tomography) – medical imaging oftumors, mapping of human brain and heart function. Most ofthe PET isotopes are short lived for clinical use & research.Using RIB it is possible to produce longer lived PETisotopes ( 72 As : T 1/2 ~ 26 hours) which are carrier free i.e.high sp. Activity.

Physics Motivation• Nuclear PhysicsStudy of nuclei away from line of β-stability• Neutron Halo ( 6,11 Li, 14 Be, 17 B, …..)• β-delayed particle emission ( 21 Mg, 16 C, 22 Al, 26 P, …)• Nuclr. Deformation & magicity ( )• Nuclear AstrophysicsZr 100 Sr80,40 38• The nuclear processes responsible for nucleosynthesis• When & where these processes took place• Chracteristics (temperature, density, composition ..) ofthe nucleosynthesis sites

Primordial NucleosynthesisThe Universe was created about 15 billion years back by gradual expansionfrom a state of extremely high density (ρ~10 95 g/cc) & temperature (T~ 10 32 K) Big Bang Theory.Nucleosynthesis could start ~ 3 minutes after the Big Bang when Deutorium(B.E. 2.23 MeV) stable against photo-dissociation at T ~ 10 9 K.Nucleosynthesis could continue for a very shorttime after the big-bang because :• All neutrons were used up for production of 4 He• No stable nuclei for A=5 and A=8• Baryon density too low for 3 body reactions• Temp. reduced due to expansion to sustainfurther nuclear reaction1H2H3He4He6Li7LiMass Fraction0.75(2.5±1.5)x10-5(4.2±2.8)x10-50.23±0.023004600+ 300 −12× 10− 150+ 4600 −12× 10− 2300

Nucleosynthesis in StarsExpandingCosmologicalgas from BigBangDensityFluctuationDenser zone willgravitationally attractmaterial from outside grows in densityWithin galaxy smaller clouds collapsedto form stars & other objectsGalaxiesFormed(t > 500 million Yrs)GravitationalCollapse of StarCore Temp. ofStar increases1H fuses to 4 Hereleasing energyRadiation pressurebalancesgravitationalcollapseHydrogen burning : Source of energy of Main Sequence Stars like Sun –continues for tens of millions of years

Nucleosynthesis in StarsElements are created in severalstages where the products of onestage become the fuel for energygeneration in the next stage.M < 8M⊕After He burning stage, star willthrow off its envelop as aplanetary nebula & become awhite dwarf.M> 8M⊕Main sequence Goes through allburning stages Red Giant Core of mostly Fe gravitationalcollapse to super-density Supernova explosion Blows offouter envelopremnant asneutron star / black holeHydrostatic burning stagesH burningHe burningC burningNe burningO burningSi burning4p ⇒ 4 He+2e + +2ν +26.7 MeVα+α ⇒ 8 Be8Be+α ⇒ 12 C+γ+7.2 MeV12C+ 12 C ⇒ 23 Na+p+2.23 MeV⇒ 20 Ne+α+4.6MeV12C(p,γ) 13 N(e + ν) 13 C(α,n) 16 O20Ne+γ ⇒ 16 O+α20Ne+α ⇒ 24 Mg+γ16O+ 16 O ⇒ 31 P+p⇒ 28 Si+α⇒ 31 S+n28Si+α ⇒ 32 S+α…+α ⇒ 56 Fe28Si+γ ⇒ α+Mg

Nucleosynthesis in StarsCNO CycleZ14 O15 OZ15 O13 N 14 N15 N13 N 14 N15 N12 C(p,α)12 C13 C(p,α)NNHOT CNOCOLD CNOA form of Hydrogen burning chain reaction takes place in non-first generationstars where C is available to start with.

Nucleosynthesis ofelements beyond Fer - Process• Rapid successive n-capture (n,g) W/O intermediate a and b - decay• Follows path closer to n-drip line• Near magic nos. nutron BE is small – b - decay occurs – path moves towardsstability line• Produces n-rich nuclei between A=56 to 270 – beyond which fission sets in

Nucleosynthesis ofelements beyond Fes - Process• Slow n-capture : slow w.r.t. b - decay process• Series of (n.g) processes and b - decays (sometimes b + and EC)• Follows path closer to the stability line• Produces n-rich nuclei between A=56 to 209 (Bi) – beyond which there are manyshort lived nuclei & slow process cannot compete.• Red giants – being a good source of neutrons from 13 C(a,n) 16 O, 17 O(a,n) 20 Ne,21Ne(a,n) 24 Mg … reactions– possible site for such processes.

Nucleosynthesis in Starsrp - Process• Rapid p-capture process : fast w.r.t. b + decay process• Follows path closer to the proton drip line• Produces p-rich nuclei up to A ~ 100 – beyond which Coulomb repulsion preventssuccessive p-capture.

Nuclear Astrophysics• Reactions involving stable nuclei drive the evolutionary stage of mainsequence stars• Reactions involving unstable nuclei dominate the outcome of explosiveeventsMajor Challenges• Number of target atoms/cm 2 is small as reactions have to be studied at avery low energy, thin targets have to be used• Expected cross section is small near or below the Coulomb barrier• Intensity of RIBs is generally less compared to stable beams• Often the RIBs are not pure (mixed beam) & have large energy spread• Background due to the decay of RIB

Nuclear AstrophysicsMajor Detection Techniques Needed• Highly segmented high efficiency gamma ray detector array• Large solid angle and good angular resolution silicon detector array• Mass separator with high beam rejection efficiency• Gas cell targets & targets of long lived radioactive nucleiGRETA (Gamma Ray Energy Tracking Array) - LBLSolid angle coverage : 0.45 0.8Detection Efficieny : 1050 %Position resolution : 20mm 2mmDRAGON (Detector of Recoils And Gammas Of Nuclear reactions)Angular acceptance ≤ ±20 mradEnergy acceptance ≤ ±4%Separation is 1 in 10 15

1.Radioactive Ion Beams will play an important role inall fields of accelerator based research for the nextfew decades2.Nuclear astrophysics is a fascinating field ofresearch of tracing back the evolution of theUniverse. It requires information of differentreactions using both stable and radioactive beams.3.But --- it requires stretching the limits of presentaccelerator and detection technologies.How to produce RIB?

Scheme of the RIB facility at VECCe-Linac50 MeV, 100 kWK=130 Cyclotron (p,a ; E=20, 60 MeV)Thick TargetIon SourceTwo Ion Source (Surface Ionisation - ECR),He-jet Two Stage Skimmer ECRIsotope Separator / LEBTnewnew1.0 keV/u86 keV/uRFQREBUNCHER35 MHz, 4-Rod Structure35 MHz, λ/4-ResonatorLINAC35 MHz IH LINAC CAVITIES : # 1 , 2 & 3450 keV/uCh. Stripper q/A = 1/16 → 1/8LINAC70 MHz IH LINAC CAVITIES : # 4, 5 & 61.3 MeV/u4-5 MeV/u(10 5 -10 9 pps)

VECC RIBfacility layout1.5 keV/u460 keV/uDec 200898 keV/uReadyExisting facility180 keV/uReady29 keV/uBeingorderedReadyReadyUnderconstruction

RF inj. lineECRFC1D1FC2SolRFQQ1, Q2FC3D2FC4

Thick target development :Selection of suitable target materialThermoCalc, Chemsage, HSC(Data based thermo-chemistry & thermodynamic codes)High dissociation temperature and low vapour pressure Optimisation of the target geometryAnalysis of time dependent diffusion rate solving Fick’s second equationfor different symmetries like planner, cylindrical and sphericalOptimising target thicknessHeat deposition in the target iscalculated using TRIM – heat depositionwithin the target sharply increases nearthe Bragg peak window.dE/dx (MeV/mm)3002502001501005060 MeV α on Al 2O 300 10 20 30 40Target Thickness (mm)

Thick target development : a → Al 2 O 3 ( T=2072° C) Temperature distribution(ANSYS)E/I : 60 MeV / 1 mA0.75 cm f x 2cm LongThe critical temperature isdetermined from critical vapourpressure Maximise surface to volumeratio of the target i.e. porous /fiber like target matrix

Thick target R&D : first few targetsCarbon* , Al 2 O 3 , ZnO, HfO 2 , BN, LiF, MgO, CaCl 2 , ThC 2 , UC 2 , ZrO 2SEM of Al 2 O 3 & HfO 2SEM of RVCFSEM of RVCF + Al 2 O 3*RVCF : Reticulated Vitreous Carbon Fiber

R&D Initiative on ion source :• Aim High On-line Efficiency for high charge States (q/A> 1/14)• Apparent Choice ECR ion sourceProblems‣ Poor vacuum (target evaporation) high q !!!‣ Neutron damage of permanent magnetsPossible solutionTwo ion source philosophyPrincipleTwo I.S. in cascade – EBPIS & ECR in our caseFirst I.S. provides q=1 + even in poor vacuumTransported to ECR at a distance to get high q(Better vacuum and acceptable n-flux)

R&D Initiative on ion source :Integrated Target-ion source1 + RIB ECR ion-source n + RIBEinzel LensFaradayCupDeceleratorµ−waveLCW1 + Plasma n+1 + Ion-SourceGuard ringSupportgasTuningelectrodeECR Ion-SourceDecelerate 1 + ions ~20 eV to ensure soft landing within ECRISChallengesOptimised focussing to prevent beam lossvECRIS : at safe distance ~ 10 -6 mbar vacuum inside plasma chamberv ECR permanent magnets protected from high radiation near target

R&D Initiative on ion source :Integrated Thick-Target Electron Beam Plasma Ion-SourceTargetEBPISPrimarybeam1+ RI beam

R&D Initiative on ion source :PrimarybeamThick targetsHeat shieldRadioactiveatomsCurrentleadTowardsEBPISTarget holder

R&D Initiative on ion source :FrequencyKlystron / Sol. PowerB ECRB Z (Inj) / B Z (Ext) / B r(r=R)Mirror Ratio (Inj/Ext)6.4 GHz3 / 60 kW0.23 T0.95 / 0.7 /0.7 T5.9 / 4.375

Typical Oxygen spectrum from ECR ion-sourceO 3+ 69 mARF= 254 WV ext= 10 kVV EL= 8.6 kV9.6x10 -7 mbarN 3+ 9.2mAN 2+ 11.5mAO 4+ 42 mAO 2+ 54 mAH 2O 1+O 5+ 6 mA

12 C 4+56 Fe 12+ /N 3+ H2O 1+ 12 C 3+O 3+56Fe 10+ 12 C 2+56Fe 9+ 56 Fe 8+ /N 2+56Fe 6+56 Fe 7+ / O 2+56Fe 5+ 12 C 1+13C 1+ N 1+ / 56 Fe 4+O 1+1086420First Iron spectrumDate:05/09/07RF Power=300WVext=10 kVVezel=11.3 kVDipole Current (arb. units)Ferrocene C 5H 5FeC 5H 5Beam Current (eµA)

Design & Development of LEBT section between on-line ECRIS & RFQK=130 Cyclotron (p,a ; E=20, 60 MeV)Thick Target1.0 keV/uIon SourceLEBT SectionTwo Ion Source (Surface Ionisation - ECR),He-jet Two Stage Skimmer ECRRFQRIB86 keV/u37.6 MHz, 4-Rod StructureDesign Aims :• Initial separation of the RIB of interest having optimum q from the rest.• Transverse matching of the selected RIB to the acceptance of the RFQ.Challenges :• Maximum transmission & RP even with high emittance beam from IS (ECR).• Minimum floor space & number of optical elements.

ECRISLow Energy Beam Transport sectionFocalPlaneMatchingsectionSolenoid length 0.25 mSolenoid Radius 0.65 mMax. Field 0.65 TRFQVirtualSourcepointErect Ellipsee = 120 π mm mrad(± 1.2 cm / ± 10 mrad)Bending Angle 90°Bending Radius 0.5 mMax. Field 0.25 TEntry / Exit angle 27.141° / 27.107°

Dispersive PlaneOptics for the analysing section of the LEBT design30X’ [mr]X [mm]-20 20Dipole-30Non-dispersive PlaneConfigurationAcceptanceDrift-Dipole-Drift120 π-mm-mr. (FullTransmission)System Length2.855 m1.07 mDipole30 Φ1 mDispersionMass R. PowerMagnification1.98 m (for 100%rigidity change)43 (3 rd order)-0.95

Optics for the LEBT sectionDispersive Plane125X’ [mr]X [mm]-6 6Transmission 98.8 %Non-dispersive Plane85 Φ30 ΦSolenoid-125125Y’ [mr]Y [mm]-6 61 m1.07 m Dipole1.48 mSolenoid.525 m-125

Design of Radio Frequency Quadrupole (RFQ)Design Aim : Acceleration of RIBs (q/A≥1/16) from 1 keV/u to about 90keV/uRFQ : Single RF structure capable of bunching, focussing and acceleratinglow energy ( ~ keV) ionsHowever Designing Machining and aligning

Vane machiningVane profile from PARMTEQ⇓Co-ordinates of Surface⇓3D modelling of profile⇓Optimum tool path generation⇓Machining of vane⇓Check co-ordinates (CMM)&surface finish (Talysurf)Requirement∆/r 0≤0.5% for goodtransmission : ∆∼30µmSkin Depth d~11 mmRt ≤ 2.2 mmsample vaneSample vane~20 mm~2mm39

RADIOFREQUENCY QUADRUPOLE (RFQ) : 1 st in IndiaRFQ during installation

Experimental Results:Test Beam: Ar 4+Calculated magneticstrength (kG)(29.06 keV/u)Q1: -1.528Q2: 1.065Q1 : -1.07Q2: 0.7D2 : 2.058Experimental magneticstrength (kG)Q1: -1.53Q2: 1.057Q1: -1.058Q2: 0.82D2: 2.058TransmissionEfficiency* %*with electronsuppression~81%FC3/FC2~80%FC4/FC241

Beams available from the RIB facility♦ Oxygen : up to 120 keV (after ECR); 464 keV (after RFQ)♦ Nitrogen : up to 100 keV (after ECR); 406 keV (after RFQ)♦ Argon : up to 160 keV (after ECR); 1.16 MeV (after RFQ)♦ Iron : up to 220 keV (after ECR); 1.6 MeV (after RFQ)♦ Also H, Helium, O2, Carbon, …Typical measured currents: O 3+ ~ 70 µA; O 4+ 40 µA; O 5+ ~ 6µA;Ar 4+ ~ 4 µA; He 1+ ~ 100 µA; Fe 6+ ~ 7 µA; Fe 10+ ~ 1 µAoptimization of ECR continuing

f_measured = 37.6 MHzQ_measured = 48003.4m RFQ duringinstallation

Design of LINAC cavitiesK=130CyclotronThick Target1.0 keV/u86 keV/u460 keV/uIon SourceIsotope SeparatorRFQLINACDesign Parameters‣q/A ≥ 1/14‣e n≥ 0.5 p-mm-mr‣ T in= 86 keV/uBeam Dynamics :Design goalsMaximising TransmissionEnergy tunabilityGood beam quality (DE, Dt)RF Analysis : Getting the desired frequency Optimisation for best shunt impedance Surface current density at the junction oftwo components should not be high

IH - LINAC :RidgeStemExcitation mode :TE111 or HDriftTubeL RL EL EL I L I CavityMagnetic FluxElectric fluxRF Current

VECLIN Snap shotε x/y= 0.5 π mm mrad & ε z= 10 π-deg-% A=16Inter-tank space 75 cmQuads L=21+14+21 cm / Aperture rad 2.85 cm / Gradient 30 T/m

IH - LINAC : The design details6. Engineering Analysis ANSYSStructural deflection under various loads :(a) Atmospheric pressure (b) Self weight (c) Thermal flux due to RFAxialdeflection offlangeRadialdeflection ofcavity

IH - LINAC : The design details Structural DeflectionThe effects have been tried to minimise using :(a) Proper thickness of the cavity materials :Mild Steel – 25 mm (cavity) & 35 mm (End covers)(b) Circular stiffeners on end covers : Two Nos.(c) Cooling108.785596.676384.6670VerticalDeflection (mm)72.560.448.3578486393Axial Deflection(mm)36.230124.220812.11160.024

IH - LINAC : The design details Temperature DistributionY54.32XZ52.1851.0150.0349.2647.8847.5245.7345.7743.5944.0341.4442.2839.2940.5437.14Z38.79Y34.99 X37.0535.3042.842.241.540.940.339.639.038.437.837.1Temperature [°C]46.145.144.143.142.141.040.039.038.036.9

LINAC-1 : Important ParametersFrequencyMHz37.6q/AT in T out 98.785 183.56keV/u≥ 1/14β in β out %1.456 1.985Accelerating gapsDrift tube I/D & O/DDrift tube gapCell legthPeak D.T. voltageMax. FieldTransit FactorSync. PhaseCavity LengthAccln. GradientShunt ImpedanceQ-ValuePower#mmmmmmkVDegreeMMV/m per qMΩ/mkW925 & 69.529.258.4 78.8101.24 kV1.4 x E Kilpatrick0.789 0.843-240.61822.10234213765~ 15

Linac -1duringtestingstemoctagonalcavity37.4654.55 84.7 92.8ridgedrifttubesWell separated modes !CAVITY :• 25 mm thk. SS304L• cladded with 5 mm thk. Cu• Diameter ~ 1.7m ; Length ~ 0.6 m1.7mf calc= 37.695 MHzQ Meas=8073 ~ 59%37.750 MHz

LINAC-2 : Important ParametersFrequencyMHz37.6q/AT in T out 183.56 286.8keV/u≥ 1/14β in β out %1.985 2.481Accelerating gapsDrift tube I/D & O/DDrift tube gapCell legthPeak D.T. voltageMax. FieldTransit FactorSync. PhaseCavity Length (Inner)Accln. GradientShunt ImpedanceQ-Value (Calc.)Power (Calc.)#mmmmmmkVDegreeMMV/m per qMΩ/mkW1025 & 6039.879.6 98.4107.5 kV1.3 x E Kilpatrick0.8045 0.8506-250.8711.7943218856~ 10

First few beams IRIB==10IPri−6RIB T1/2 Production Target11C13N17F18F19Ne35Ar38K90Kr93Rb⋅Nt⋅ σ ⋅20 min10 min1 min110 min17 sec1.7 sec7.6 min32 sec6 secηrelease⋅ηIS11B(p,n)13C(p,n)14N(α,n)16O(α,n)19F(p,n)35Cl(p,n)⋅ηseparation35Cl(α,n)U/Th(α,f)-do-BNGraphiteBNHfO 2,Al 2O 3LiFCaCl 2CaCl 2UC/ThO-do-⋅ηtransport( ) ( 23) ( −3−24) 9⋅ 6⋅10⋅ 50⋅10⋅10⋅ 0.1⋅0.05⋅0.6⋅0.5 ≈ 10 pps−191.6⋅101mA 1g/cm 2 50 mb0.15%Expected average yield at experimental station ~ 10 6 -10 829

Future Plans

LINAC : What Next ???LINAC-1 : 98.785 183.56 keV/u• Installation at VECC have started : To be completed by 15 th Oct, 2007• Installation in beam line : April 2008LINAC-2 : 183.6 286.8 keV/u• PO placed• Delivery schedule : Mar 2008• Installation in beam line : Sep 2008LINAC-3 : 286.8 450 keV/u• Advanced stage of design• Likely completion date : Dec 2008LINAC-4 to LINAC-8 : (To be completed by 2012)• Frequency 75.2 MHz• 450 keV/u to 1.3 MeV/u• Physics design stage

e-linace- γUraniumISOL type RIB facilityRIB50 MeV,100 kWTatargetUC 2targetγ- induced fission (photo-fission); GDR peak at ~13.5 MeVaverage photo-fission cross-section = 160 mbExpected yield of some very neutron-rich exotic nuclei at target78Ni : 2 x 10 9 pps; 132 Sn : 2 x 10 11 pps91Kr: 1 x 10 12 pps; 94 Kr: 3 x 10 10 pps58

Recent publication from RIB project group(in international peer review journals)1. Phys. Lett. (in press), 2007. Experiments2. Nucl. Instrum. & Meth. B261(2007)1018. RIB facility status3. Rev Sci Instrum. Vol78 (2007) 043303. RFQ results4. J of Phys. Condensed Matter 19, (2007) 236210. Experiments5. Ceramics International, (in press). Target6. Nucl. Instrum. & Meth. VolA560 (2006)182. Linac design7. Nucl. Instrum. & Meth. VolA562 (2006)41. Beam-line8. Nucl. Instrum. & Meth. VolA539 (2005)54. Target9. Nucl. Instrum. & Meth. VolA547 (2005)270. Charge breeder design10. J. of Mat. Sc. 40 (2005) 5265. Experiments11. Nucl. Instrum. & Meth. VolA535 (2004)599. RFQ design12. Physica C, Vol416, (2004) 25. Experiments13. Nanotechnology 15 (2004) 1792. Target14. Nucl. Instrum. & Meth. VolA447 (2000)345. Charge breeder design59

Thank You!60

VEC CyclotronElectron-LINACTarget – Ion – SourceMaterial Sciencewith stable & RIBeamsIsotope SeparatorRFQ (98 keV/u)Spectroscopy ofr-process, n-richexotic nucleiLINACs1.3 MeV/uNuclearAstrophysicsexperimental stationScatteringchamberElastic & In-elasticscattering studieswith RI beams61

238U photo-fission fragmentsmass distributionfission yield per electron for 238Uas a function of electron energy62

IH - LINAC : The design details Beam QualityBetter Intensity (95% transmission) Better Beam Quality4820∆E(%)321642ε_z(p . Deg . MeV/u)*1E-3ε z∆f∆T DE15105δφ_max(Deg)000 100 200 300 400 500Length [cm]00 100 200 300 400 500Length [cm]Better Intensity (95% transmission) Better time structure (66% transmission)εz-rms : increased by 2.5 times No change∆E : No change 2.8 1.9% (2*rms energy width)63Df : 4.06°2.23° 4.06°1.34°(2*rms phase width)

IH - LINAC : The design details Possible set of energy tunesKnobs : RF voltage & phaseEnergy (keV/u)263 – 397.5158.2 – 263100 – 158.2Tank-1Design DesignDesign KnobsKnobsCaptures >90% of beamTank-2OffTyp. Energy widths ~ ± 0.5-1%Typ. time widths ~ ± 1 nSTank-3KnobsBuncherBuncher2*∆Φ_rms2*(∆T/T)_rms∆φ [Deg]∆T/T [%]φ-φ s [Deg]Voltage & Phase settings3025201510503.02.52.01.51.00.50.0400-40-80Energy Tunability-120100 150 200 250 300 64 350 400Beam Energy [keV/u]Tank-3Tank-2Tank-1