From simulations to an operating cyclotron The story of the K130 cyclotron

Transcription

1 From simulations to an operating cyclotron The story of the K130 cyclotron Pauli Heikkinen University of Jyväskylä Finland Uppsala May, 2018

2 Pre-historical time MC20 from SCX ( ) Proposal for a superconducting K800 Cyclotron A copy of the Milan K800 cyclotron (later installed in Catania) The proposal was finally rejected in the State Budget (Ministry of Education) during the very last handling of the budget in mid 80 s New proposal for a cheaper cyclotron

3 Normal conducting cyclotron A multi-particle, variable energy cyclotron with K = MeV An MC106 from Scanditronix was chosen Later, due to another request from Japan, MC106 was changed to K130 The first of its kind by Scanditronix Needed to be designed A model magnet vs. computer simulations

4 Magnet design During the superconducting cyclotron project, methods to calculate 3D magnetic fields were learned High magnetic field Saturated iron Easy to separate the average and sector fields Normal conducting cyclotron B < 2 T Iron not saturated TOSCA vs. a semi-3d method

5 To pay or to develop? That was the question TOSCA Existing program Expensive Proven method Semi-3D To be developed Cheap risky The method was developed using MC40 drawings and measured fields Blind-tested with MC50 drawings without measured fields Accepted

6 A Semi-3D method Calculate the azimthally averaged median plane field with a 2-D program (Poisson) Sectors treated using Radially dependent stacking factor or Calculating the field with 100% hills and without hills Add the azimuthally wighted difference field to field without hills to get the true averaged field

7 Cylinder symmetric model

8 Aveage field at 1000 A

9 Coil current correction Note! Iron starts to saturate

10 Average field at 150 A

11 Calculate the azimuthally varying component using surface currents For a fully saturated iron, surface currents only on vertical sector edges Surface current density M = 2.14 T/m 0 = 1.7 x 10 6 A/m For non-saturated iron, use M = B(hill)/m 0 along sector edges and a linearly (or step-wise) decreasing surface current density following the sector edge inside the pole up to depth to be fitted with a 2-D model. Take only the AC component of the sector field and add to the azimuthally averaged field.

12 Rectangular sector model The approximated surface current density along the positions of the sector edges are fitted to the Poisson solution Only one variable to be fitted The same axial current dependence is used for the actual sector geometry Calculated using Biot-Savart law

13 Harmocic field components at 1000 A

14 Flutter at 680 A

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17 Is the calculated field accuracy Average field enough? Multi-particle, variable energy machine Average field finally adjusted by trim coils to get an isochronous field Average field optimized to minimize maximum trim coil power Azimuthally varying field Maximum proton energy (focusing limit) most critical Need for an accurate Flutter Very exact calculated Flutter at extraction region (OK)

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24 E m c k 0 m c 2 0 2

25 Injection External ion source Matching the beam into the cyclotron s Central region acceptance Accelerated equilibrium orbit eigen ellipses Low-energy beam Possible space charge limitation

26 Nose for the 1st harmonic mode for optimal RFphase Electric focusing important in the first gaps -> Central region design

27 Spiral inflector Beam bending without magnetic field a) Cross-section of the spiral electrodes and b) beam projection on xy plane

28 Injection has an effect on beam behaviour in the cyclotron Probe Beam Effective probe width Differential probe scan with a) a changing effective probe width and b) with a constant effective probe width.

29 The beam rotates at the radial betatron frequency Match the beam into the acclerated equilibrium orbit eigen ellipses with quadrupoles (4) Center the beam

30 Passive focusing channels Electromagnetic channel Deflector Central region + inflector

31 Bump with a harmonic coil <B harm >=0 Contribution of harmonic coils in three valleys Precession after n r =1 resonance

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33 Equilibrium orbit Stable Unstable Radial phase space without a 1st order perturbation

34 Radial Phase space with a 1st order perturbation Opening in the stable phase space

35 Phase and amplitude of the perturbation is important!

36 Phase and amplitude of the harmonic perturbation important Implication: Centering of the beam is also important!

37 Note: Mono-energetic beam was started from the equilibrium orbit in this tracking! Single turn extraction: Well centered beam Small RF phase width -> phase slits Nice behavior with a proper 1st harmonic perturbation

38 Extraction elements (Harmonic coils) Electrostatic deflector Electromagnetic channel (Passive) focusing channels

39 Electrostatic deflector Negative high voltage Gap: a few mm s

40 Electromagnetic channel Electrostatic deflector

41 V-shape entrance for the septum effective thickness 0 mm Distribute heat

42 Electromagnetic channel

43 High current in the EMC coil Main coil current + booster current

44 Minimize B at resonance

45 Passive focusing channel Vertically focusing Horizontally focusing Iron bars are magnetized by the cyclotron magnetic field

46 Focusing channel Extracted beam travels in the fast decreasing fringe field Horizontally defocusing More focusing by shaping the field (gradient) by passive channels

47 Accelerator Laboratory, Department of Physics, University of Jyväskylä Stripper Since August 2000, H - & D - 4 carbon foils (16x22 mm) thickness 1 and 2 mm

48 K130 Accelerated elements: p Xe E = Q 2 /A 130 MeV Ion sources: 6.4 GHz ECRIS 14 GHz ECRIS 18 GHz ECRIS Multicusp (H -, D - )

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50 Maintenance

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55 Ferrites Coupling capacitor

56 Ferrites for filtering

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58 RF tube

59 JYFL Accelerator Laboratory Four accelerators serving international users for basic research, applications and commerical services: K130 heavy ion cyclotron (+ three ECR ion sources and light ion source) (1992) 1.7 MV Pelletron for ion beam analysis and modification of materials (2007) MCC30 light ion cyclotron (2012) Electron LINAC (2015) Integral part of the Department of Physics National centre for accelerator-based research and education Centre of Excellence of the Academy of Finland ( ) EU access laboratory (FP4 Horizon2020) On the roadmap of research infrastructures (RI) in Finland The only operational RI in the Natural Sciences and Technology category One of the three recognised test laboratories of European Space Agency (ESA) Typically 300 foreign users annually International instrumentation investments of >10 M Total staff 68: 50 in research groups, 18 in Accelerator and Mechanical/Electrical Workshops Total budget approximately 6-7M (roughly 50% JYU / 50% External) Strong links to research at CERN and FAIR

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61 JYFL

62 K130 cyclotron MCC30/15 cyclotron Department of Physics (Old) experimental hall Extension of the laboratory

63 reunaviva 20 dipolin mukaan asetettuna reunaviva K130 yoken mukaan asetettuna Accelerator laboratory Pelletron Commercial applications Medical Reactions ECR MARA RITU *RADEF -Space -Microfilters -CLinac BB2 QB7 K=130 MeV Medical K=30 MeV IGISOL m *RADiation Effects Facility

64 RDT with JUROGAM + RITU + GREAT Focal plane Detectors GREAT Separator RITU JUROGAM Ge array Transfermium nuclei Shape coexistence: light Pb, Po nuclei Proton dripline Collectivity close to 100 Sn N=Z nuclei, A = TDR Total Data Readout

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66 MARA VACUUM MODE SEPARATOR better mass selection in RDT experiments ED Focal plane MD QQQ Beam Solid angle acceptance (central m/q and energy) 10 msr Typical transmission ~12% per charge state 1st order resolving power ~260 J. Sarén, PhD thesis, University of Jyväskylä (2011)

67 MARA VACUUM MODE SEPARATOR The new vacuum mode separator MARA better mass selection in RDT experiments QQQ Beam Solid angle acceptance (central m/q and energy) 10 msr Typical transmission ~12% per charge state

68 RADiation Effects Facility RADEF ISS Official test laboratory of ESA since 2005

69 Radef cave including LINAC Foil beaming e - 6,9,12,16 or 20 MeV Brehmstrahlung X-rays 6 or 15 MeV

70 IGISOL-4: Next generation K=30 MeV cyclotron Target and ion guide setups from K=130 MeV cyclotron Unique instrumental combination of: IGISOL-technique applied for different reactions Ion trap technology Laser techniques for spectroscopy, resonant ionization and ion beam manipulation Decay stations with in-house and foreign setups 30 years of reseach of exotic nuclei, especially their groundstate properties and decay modes. Decay station Mass spectrometry & post-trap spectroscopy Collinear laser spectroscopy

71 MCC30/ ma protons 62 ma deuterons

72 MCC30/15 Stripper Valley Hill

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75 1 st Anniversary of K130