Acceleration of RIB using linacs Moriond Meeting 17-21/3/2003 Acceleration of RIB using linacs Alberto Facco INFN-Laboratori Nazionali di Legnaro Contents Introduction Technological highlights in superconducting low- linacs Superconducting linacs for RIB acceleration Example of multicharge transport in EURISOL SRL Conclusions

Ideal RIB accelerator requirements Moriond Meeting 17-21/3/2003 Ideal RIB accelerator requirements Acceleration of all possible radioactive beams All possible final energies up to ~ 100 MeV/u, finely tuneable Capability of acceleration of singly charged ions Very good beam quality up to at least 10 MeV/u Affordable construction and operation cost reliability, easy maintenance, easy beam set-up and operation, etc.

RIB accelerators special constraints Moriond Meeting 17-21/3/2003 RIB accelerators special constraints Variable q/A beams Efficiency in a wide range of q/A Wide acceptance in : acceleration with variable velocity profiles is desirable Very low current beams negligible beam loading: Rf power efficiency Stability and large acceptance Very high transmission efficiency, aiming to 100%

Independently-phased Superconducting Cavity Linacs virtues Moriond Meeting 17-21/3/2003 Independently-phased Superconducting Cavity Linacs virtues Wide velocity and q/A acceptance Modularity: all final energies can be reached, with fine tunability Excellent beam quality Transmission efficiency limited only by charge selection after stripping Recent achievements in the field: high transmission efficiency after stripping Competitive construction and operation cost Multicharge beam transport High acceleration gradient

Technological highlights in superconducting low- linacs Moriond Meeting 17-21/3/2003 Technological highlights in superconducting low- linacs

Superconducting QWR’s Moriond Meeting 17-21/3/2003 Superconducting QWR’s (optimum range 0.03<<0.3 and 50<f<200 MHz) Mechanical damper LNL 80 MHz, =0.055 cryostat Best ALPI and PIAVE low beta cavities results LNL PIAVE 80 MHz,  =0.047 QWR

ISAC-II =0.072 cavity Design gradient: 6 MV/m @7W Moriond Meeting 17-21/3/2003 ISAC-II =0.072 cavity Design gradient: 6 MV/m @7W reached 7 MV/m with <10W TRIUMF ISAC-II 106 MHz, =0.072 prototype 4.2 k test results

Superconducting Spoke resonators Moriond Meeting 17-21/3/2003 Superconducting Spoke resonators (optimum range 0.2<<0.5 and f350 MHz) ANL =0.3 and = 0.4 prototypes LANL =0.2 prototypes

Superconducting RFQ’s Moriond Meeting 17-21/3/2003 Superconducting RFQ’s Compactness CW operation High efficiency LNL Superconducting SRFQ2 A/q=8.5, 0.0255<b<0.0355

Low - SC linacs design gradient Moriond Meeting 17-21/3/2003 Low - SC linacs design gradient 6 MV/m already achieved in existing linacs 7 MV/m seems very realistic for future accelerators

EM steering in QWR’s The steering is proportional to the energy gain Eurisol Town Meeting, Abano 24-25/1/2002 EM steering in QWR’s The steering is proportional to the energy gain The magnetic contribution is dominant

Quarter Wave Resonators with dipole correction A. Facco - SPES meeting –LNL 11-3-2003 Quarter Wave Resonators with dipole correction ANL QWR 115 MHz for RIA MSU QWR 161 MHz for RIA (MSU-LNLcollaboration) QWR steering : 161 MHz standard shape (top) 161 MHz corrected

Multicharge beam transport Moriond Meeting 17-21/3/2003 Multicharge beam transport Proposed and demonstrated at ANL (in ATLAS) Studied at ANL and MSU for RIA (driver and reaccelerator linacs) TRIUMF for the ISAC-II reaccelerator LNL for the Eurisol reaccelerator Important tool to achieve high efficiency in both transmission and acceleration

Multicharge beam transport Moriond Meeting 17-21/3/2003 Multicharge beam transport q1 q2 q3 q4 f W Ions with different charge state receive the same acceleration if their synchronous phase is properly chosen Many different charge states can be transported simultaneously Most of the beam particles can be captured after stripping DW=qEaLT(b)cosf

Multicharge beam transport Moriond Meeting 17-21/3/2003 Multicharge beam transport F=-150 F=-1000 F=-200 beam Phase synchronization after the first stripper, at the beginning of the SRL ME section. Top: first cryostat (see fig 3) and the reference acceleration phase at each of the cavities. Bottom: longitudinal phase space, in energy spread (%) as function of phase (deg) in different position along the cryostat. The cavities frequency is 160 MHz. The 5 charge states of the beam particles are represented by different colors.

Examples of superconducting linacs for RIB acceleration Moriond Meeting 17-21/3/2003 Examples of superconducting linacs for RIB acceleration

ISAC post-accelerator at TRIUMF (operating, under completion) Moriond Meeting 17-21/3/2003 ISAC post-accelerator at TRIUMF (operating, under completion) ISAC-I, in operation NC Linac up to 1.5 MeV/u ISAC-II, under construction SC linac ~43 MV Rib energy up to ~6 MeV/u A150 1 or 2 carbon foil strippers Multicharge transport Charge breeder for A>30

ISAC post-accelerator special components Moriond Meeting 17-21/3/2003 ISAC post-accelerator special components 35.3 MHz RFQ A/q 30 (8m long) 106 MHz Separate function DTL SC QWRs 70.7 MHz =0.042 106 MHz, =0.072 (under construction) 106 MHz =0.105 ANL-RIA type SC solenoids Inside cryostats

The RIA RIB facility RIA Driver SC linac: Ion beams of all masses Moriond Meeting 17-21/3/2003 The RIA RIB facility RIA Driver SC linac: Ion beams of all masses 400 MeV/u Uranium RIA driver superconducting cavities under development at ANL RIA (MSU version)

Moriond Meeting 17-21/3/2003 The ANL-RIA post-accelerator (proposed as injector of the existing ATLAS SC linac) No charge breeder, accepting q=1+ Masses 66<A< 240 need He gas stripper at ~10 keV/u to reach A/q66 Carbon foil stripper at 600 keV/u to reach A/q8.3 3 NC RFQs (2 on a 400 kV platform) 62 SC cavities + SC solenoids Output energy 1.4 MeV/u Very efficient in transmission, >30% up to the 2nd stripper Good emittance Very conservative design gradient Beam injected into ATLAS ( ~50 MV)

RIA post-accelerator special components Moriond Meeting 17-21/3/2003 RIA post-accelerator special components R&D in an advanced stage for RFQ and SC solenoids 4-gap SC cavity technology well established ATLAS working since 20 years 15 T superconducting solenoid with steerers 4 gap superconducting QWR 12 MHz Hybrid rfq

EURISOL SRL (preliminary project) Moriond Meeting 17-21/3/2003 EURISOL SRL (preliminary project) 2 intermediate stripping stations to increase linac efficiency and reduce linac length 3 main extraction lines for low, medium and high energy experiments Multicharge beam transport to maximize transmission up to 100 MeV/u Acceleration with no stripping and full intensity up to 60 MeV/u

SRL cavity parameters QWR HWR * Calculated by means of the code HFSS Moriond Meeting 17-21/3/2003 SRL cavity parameters QWR HWR Cavity type QWR HWR units f 80 160 240 320 MHz b0 0.047 0.055 0.11 0.17 0.28   Ep/ Ea 4.89  4.81  4.93  5.17  3.7 Hp/Ea  103  101  108  110 106 Gauss/(MV/m) G= Rs  Q  14.9  28.3  38.4  61.7 W Rsh / Q  1640 1660 1480  1470 1200 W/m U/ Ea2 0.121 0.120  0.0670  0.0452  0.093 J/(MV/m)2 Eff. length 0.18 0.223 m Design Ea 7 MV/m Cryo power allowed 10 n. required 3 15 24 37 * Calculated by means of the code HFSS

SRL modules SRFQ section QWR-HWR modules Moriond Meeting 17-21/3/2003 SRL modules Schematic of RFQ section and first QWR module SRFQ section 3 LNL type superconducting RFQ’s in 2 cryostats Design A/q  10 (up to 132Sn13+) Ein =2.3 keV/u, Eout =670 keV/u QWR-HWR modules Cryostat 4 QWR’s (section I and II) at 7 MV/m 8 HWR’s (section III) at 7 MV/m 1 superconducting solenoids at B<15 T Diagnostics box

Example of multicharge beam transport in EURISOL SRL Moriond Meeting 17-21/3/2003 Example of multicharge beam transport in EURISOL SRL

Beam dynamics simulations in SRL* using realistic EM fields of QWR’s Moriond Meeting 17-21/3/2003 Beam dynamics simulations in SRL* Simulation of the accelerating sections using realistic EM fields of QWR’s Aims: Check multiple charge beam transport at high gradient Check the effect of QWR steering in MCBT Evaluate SRL performance in different operation modes No stripper up to 60 MeV/u 1 stripper 93 2 strippers 100 * performed using the code LANA (courtesy of D. Gorelov, MSU-NSCL)

Linac Beam Envelopes with no strippers Moriond Meeting 17-21/3/2003 Linac Beam Envelopes with no strippers Simulated using the LANA code 132Sn Win= 670 keV/u Wout= 59.6 MeV/u f = -20 deg Eacc= 7 MV/m q Eff. (%) Cav./prd. I 25 100 4 II III 8 N.B. simulation performed with an input transverse emittance 2 times larger than the nominal value

High Energy Section-160 HWR’s (1 stripper mode) Moriond Meeting 17-21/3/2003 High Energy Section-160 HWR’s (1 stripper mode) INITIAL* FINAL Simulated using the LANA code 132Sn Win= 16.3 MeV/u Wout= 92.9 MeV/u = -20 deg q=45,46,47,48,49 Eacc= 7 MV/m Eff.= 94% BUNCHED * After stripping in a 2 mg/cm2 carbon foil N.B. simulation performed with an input transverse emittance 2 times larger than the nominal value

Linac Beam Envelopes with 2 strippers Moriond Meeting 17-21/3/2003 Linac Beam Envelopes with 2 strippers Simulated using the LANA code 132Sn Win= 670 keV/u Wout= 100 MeV/u f = -20 deg Eacc= 7 MV/m q Eff. (%) Cav./ prd. I 25 100 4 II 36,37,38,39,40 78 III 46,47,48,49 95 8 N.B. simulation performed with an input transverse and longitudinal emittance 2 and 5 times larger than the nominal value, respectively

High Energy Section-160 HWR’s (2 stripper mode) Moriond Meeting 17-21/3/2003 High Energy Section-160 HWR’s (2 stripper mode) INITIAL* FINAL Simulated using the LANA code 132Sn Win= 21.6 MeV/u Wout= 100 MeV/u = -20 deg q=46,47,48,49 Eacc= 7 MV/m BUNCHED * After one more stripping in a 3 mg/cm2 carbon foil

SRL simulations results for different modes of operation Moriond Meeting 17-21/3/2003 SRL simulations results for different modes of operation No stripping (prob. most experiments) E max 60 MeV/u Transmission 100% Single charge beam ex ey  0.5(0.25) p mm mrad, ez  0.7 p keV/u ns (5 rms) Stripper 2 only E max 93 MeV/u transmission 94% Multiple charge beam ex ey  0.6(0.3) p mm mrad, ez  1.4 p keV/u ns (5 rms) Strippers 1 and 2 E max 100 MeV/u Transmission 74% Multiple charge beam ex ey  1(0.5) p mm mrad, ez  10(2) p keV/u ns (5 rms) N.B: 2 Strippers make the linac relatively insensitive to the charge breeder performance: with initial charge of 13+ instead of 25+, the final energy would be 95 MeV/u

Acceleration of different q/A beams with 2-gap cavities Moriond Meeting 17-21/3/2003 Acceleration of different q/A beams with 2-gap cavities Virtually all RIB’s that allow charge breeding can be accelerated by SRL with similar results. Examples: 33Ar(8+) E=127 MeV/u 210Fr(25+) E=100 MeV/u 33Ar(8+) 210Fr(25+)

SC linacs can be excellent RIB accelerators Moriond Meeting 17-21/3/2003 Conclusions Recent developments in SC linac technology multiple charge beam transport beam stripping and high transmission Superconducting cavites high gradients, wide b acceptance High charge breeding is not strictly necessary (but some charge breeding saves a lot of money) SC linacs can provide RIB acceleration with finely tuneable energy and good beam quality High acceleration and transmission efficiency Large acceptance in q/A low mass selectivity, but also low sensitivity to charge breeder performance flexibility in the modes of operation competitive construction and operation cost SC linacs can be excellent RIB accelerators