STATUS OF LINAC BEAM COMMISSIONING FOR THE ITALIAN
STATUS OF LINAC BEAM COMMISSIONING FOR THE ITALIAN HADRON THERAPY CENTER CNAO P. A. Posocco INFN-Laboratori Nazionali di Legnaro On behalf of the CNAO-GSI-INFN collaboration P. A. Posocco – TH 10
Welcome to CNAO (Centro Nazionale Adroterapia Oncologica) The CNAO has been conceived to perform treatment of deep seated tumours with light ion beams (proton, Carbon ions and others) and to clinical and radiobiological P. A. Posocco – TH 10 2
CNAO from outside Main building: Technical building Accelerator vault 2° floor: auditorium & library 1° floor: offices and laboratories Ground floor: Reception and med. preparation Basement: 3 treatment rooms P. A. Posocco – TH 10 3
The CNAO facility The accelerator - Compact design - 25 m diameter ring - Multi turn injection - Final energy: Carbon: 2400 Me. V Protons: 250 Me. V P. A. Posocco – TH 10 The 3 treatment rooms - 2 w. horizontal beam - 1 w. hor. + vert. beam - scanning mag. (20 x 20 cm) - ~3000 patients/year - 80% C, 20% protons 4
CNAO Injector: Sources Specifications Extraction Voltage 24 k. V Current H 3+ > 700 μA Current C 4+ > 150 μA Transv. norm emitt. (95%) 0. 5 mm mrad LINAC Specifications Operating frequency 216. 816 MHz Final beam energy 7 Me. V/u Beam pulse length ≤ 300 μs Beam rep. rate ≤ 5 Hz Transv. norm emitt. (95%) 0. 8 mm mrad Exit energy spread ± 0. 3% Total injector length ~ 19 m P. A. Posocco – TH 10 Ion source supervised by INFN LNS Low energy beam transport by CNAO Linac by GSI (second version of HICAT) supervised by INFN LNL Chopper 8 ke. V/u RFQ Sources C 4+ and H 3+ 400 ke. V/u IH - DTL 7 Me. V/u Solenoid Spectrometer Switching magnet Stripping foil 5
The Injector as it was in January 2009 Source II Spectrometer Solenoid Switching magnet Chopper RFQ 75° dipole P. A. Posocco – TH 10 6
Injector commissioning milestones from to May 08 July 08 September 08 December 08 January 09 February 09 25 th Feb. 09 12 th Mar. 09 13 th Mar. 09 3 rd April 09 May 09 June 09 now RFQ LEBT IH DTL Sources P. A. Posocco – TH 10 Section Description Source Beam and LEBT Inst. LEBT TB 0 Beam Install. RFQ TB 2 RF Cond. Beam IH DTL TB 3 Install. RF Cond. 7
Ion Sources Performances • • Improvements (in 2007) the gas injection system has been modified in order to improve the stability extraction gap distance modified to improve beam emittance and stability a lead shield 10 mm thick all around the source instead of a 5 mm one for improving radiation safety the noise of electronics has been reduced P. A. Posocco – TH 10 New extraction column Performances • 250 μA for C 4+ (25% > nominal) • 1100 μA for H 3+ (50% > nominal) plasma electrode hole diameter reduced to 6 mm allowing to have better emittance 8
LEBT Commissioning Horizontal Vertical Emitt. RMS: ~35 mm mrad C 4+ TB 0 P. A. Posocco – TH 10 9
Commissioning of LEBT TB 0 (GSI & CNAO) Farady Cup ACT (in front of solenoid) Slit-scanner Emittance chamber (length = 390 mm!) P. A. Posocco – TH 10 CNAO Faraday cup GSI End Cup 10
Emittance in TB 0 H 3 + -4 +4 > 90% inside 180 mm mrad (yellow ellipse) TB 0: • AC/DC current • AC/DC profiles • DC emittance exactly at the RFQ matching point!!! P. A. Posocco – TH 10 C 4+ 11
Matching solenoid Nominal value Example of beam steering at TB 0 grid as function of the solenoid strength Results: • Very accurate centroid displacement correction (~1 mm over 3 cm wide beam!!!) • Linear response P. A. Posocco – TH 10 Sol-002 S. Vitulli & G. Bazzano (CNAO) Sol-002 The 3 solenoids build by Sigma. Phi: magnetic field along the axis measurements at INFN Frascati 12
LEBT Commissioning summary TB 0 • Comparison current measurements (GSI/CNAO & DC/AC) – Consistency • Comparison of profiles (grid/scanner) – Consistency • Beam position as function of solenoid field – Steering at RFQ entrance • Profiles for long and short macro pulses at – Neutralisation, Space • Different times within pulse (H 3 +/C 4+) – Charge, verification of DC emittances Mandatory for RFQ good performances!!! • Transmission, Twiss-Parameter and emittances – Matching RFQ – Definition of LEBT operating parameters – Pre-condition for RFQ commissioning P. A. Posocco – TH 10 13
Commissioning of RFQ TB 2 (GSI) Faraday Cup Profile grid (from right) Mob. Emi Slits and profile grid Phase probes Beam End Cup ACT P. A. Posocco – TH 10 14
Intertank section with MEBT partly integrated in the RFQ: compact but reduced flexibility Buncher gaps 205 mm IH-DTL RFQ Beam Quadrupole magnets Steerer magnets Phase probe P. A. Posocco – TH 10 15
Commissioning RFQ – Results H 3+ at 8 ke. V/u transmission, steering and energy Step 1: Optimisation Step 2: Perform standard measurements Steerer LN-002 -ITM off QD 1= -11. 8 m-1 / QD 2= 8. 6 m-1 Transmission ~57 % at working point 5. 1 Volt (195 k. W) Moderate steering in both planes with smooth behaviour P. A. Posocco – TH 10 16
Commissioning RFQ – Results H 3+ at 8 ke. V/u Emittances in TB 2 4 rms [mm mrad] P. A. Posocco – TH 10 4 rms [mm mrad] 17
Commissioning RFQ – Results C 4+ Transmission, energy und steering Step 1: Optimization Step 2: Perform standard measurements Transmission ~62 % at working point 5. 1 Volt (195 k. W) Moderate steering in both planes with smooth behaviour P. A. Posocco – TH 10 18
Commissioning RFQ – Results C 4+ Emittances in TB 2 4 rms [mm mrad] P. A. Posocco – TH 10 4 rms [mm mrad] 19
Probe beam (H 3+) Emit. RMS: ~5 π mm mrad H 3 + Slits combined to reduce up to 10% of the full emittance!!! Horizontal Vertical M. Pullia (CNAO) profile in L 2 (~10 mm width) P. A. Posocco – TH 10 20
RFQ: Results H 3+ “probe beam” at 8 ke. V/u Steering, energy and transmission Steerer LN-002 -ITM aus QD 1= -11. 8 / QD 2= 8. 6 Transmission ~70 % at working point 5. 1 Volt (195 k. W) Moderate steering in both planes with smooth behaviour P. A. Posocco – TH 10 21
RFQ commissioning results Ion H 3 + C 4+ Energy (ke. V/u) 7. 5 8. 0 8. 5 8. 0 Working point (V) 5. 15 5. 10 Max. transm. full beam 4. 6% 58% 59% 62% Max. transm. probe beam 3. 4% 71% 69% - x rms emit. (4 rms [mm mrad]) - 18. 7 21. 6 17. 9 y rms emit. (4 rms [mm mrad]) - 14. 2 13. 7 12. 3 P. A. Posocco – TH 10 22
Effect of the bend electrodes on RFQ acc. Full beam Probe beam By S. Yaramyshev ~15% cm Measured at CNAO 30 125 150 HIT CNAO 175 (total) P. A. Posocco – TH 10 23
Exp. RFQ acceptance at 8 ke. V/u ± 15 mrad!! xc= -1. 4 mm yc= -0. 1 mm x’c= 3 mrad y’c= -10 mrad M. Pullia (CNAO) et al. Probe beam displaced in position and angle with L 2 steerers By S. Yaramyshev P. A. Posocco – TH 10 24
Commissioning RFQ Summary results • Working point: – Energy of 400 ke. V/u reached at 195 k. W power • Steering RFQ and quadrupole doublet: – Size acceptable and smooth behavior – during operation only small correction with steerers – very small beam losses in inter-tank section! • Currents: – ~500 µA (H 3+) – ~75 µA (C 4+) – transmissions up to 60 % • Transverse emittances: – H 3+ : Hor - Ver(90%) = 19 / 14 π mm mrad – C 4+: Hor - Ver(90%) = 18 / 12 π mm mrad – within acceptance of IH-DTL (~50 mm mrad) • RFQ operating parameters: – Established for H 3+ and C 4+ beams P. A. Posocco – TH 10 25
Commissioning RFQ Summary of further measurements • Variation of LEBT energy: Measurements with 7. 5, 8. 0 and 8. 5 ke. V/u – At 7. 5 ke. V/u no useful results – At 8. 5 ke. V/u results are similar to 8. 0 ke. V/u case but at higher RFQ power level • Stability of energy over 1. 5 h: – variation in 2 ke. V/u region • Measurement (Hor. and Vert. ) of RFQ acceptance at 8. 0 and 8. 5 ke. V/u: – both measurements consistent • Optimization of LEBT settings with respect to centers of measured acceptance – higher transmission – reduced steering and emittance after RFQ • WHY ONLY 70% TRASMISSION AT MAX, with pencil beam ? – Probably longitudinal losses, the RFQ is not able to capture and accelerate more than 70% of particles even for on axis particles! P. A. Posocco – TH 10 26
Now: IH – DTL! TB 3 (GSI) P. A. Posocco – TH 10 27
Thanks to all the authors • A. Pisent, P. A. Posocco, C. Roncolato, INFN/LNL, Legnaro (PD), Italy • C. Biscari, INFN/LNF, Frascati (RM), Italy • G. Ciavola, S. Gammino, INFN/LNS, Catania, Italy • G. Clemente, K. M. Kleffner, M. Maier, A. Reiter, B. Schlitt, H. Vormann, GSI, Germany • G. Balbinot, E. Bressi, M. Caldara, A. Parravicini, M. Pullia, C. Sanelli, E. Vacchieri, S. Vitulli, CNAO Foundation, Pavia, Italy P. A. Posocco – TH 10 28
- Slides: 28