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Technical aspects of the ATLAS efficiency & intensity upgrade. Peter N. Ostroumov. ATLAS Users Workshop, August 8-9, 2009. Content. Limitations of the current ATLAS configuration Efficiency of CARIBU beams High-intensity ion beams (~0.1 mA) ATLAS, >10x intensity upgrade Phase I & II - PowerPoint PPT Presentation
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Technical aspects of the ATLASefficiency & intensity upgrade
Peter N. Ostroumov
ATLAS Users Workshop, August 8-9, 2009
2P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Content
Limitations of the current ATLAS configuration– Efficiency of CARIBU beams
– High-intensity ion beams (~0.1 mA)
ATLAS, >10x intensity upgrade– Phase I & II
Phase I: ARRA funding– New CW RFQ
– New G=0.075 cryomodule
– Upgrade of LHe distribution system
Current technical developments related to AIP and ARRA– Linac design optimization
– Prototyping the cavity sub-systems
– Development of new QWR, G=0.075
– RFQ: hardware development and test
– SC cavity EM optimization and mechanical design
– Initial studies of EBIS charge breeder for CARIBU
3P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
The goal
Increase overall transmission of any ion beam including CARIBU radioactive beams to 80% as compared to the intensity of DC beam from the ion source or charge breeder
Deliver ~5 MeV/u medium-intensity (~10 pA), medium-mass ion beams for experiments related to the synthesis of superheavy elements
Increase reliability and efficiency of the LHe distribution system Deliver full ATLAS energies at beam intensities of 1 pA
PHASE I, ARRA, $9.86M project
Increase efficiency of charge breeding by using EBIS– For low intensity CARIBU beams (≤107 ions/sec) the efficiency can reach
~15% Produce and accelerate stable ions to 6-16 MeV/u (depending on Q/A)
with intensity up to 10 pA Increase existing ATLAS capabilities for low-intensity ion beams with
improved acceleration efficiency (beam energies from 10.2 to 26 MeV/u)
PHASE II, additional $35M
4P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Efficiency and Intensity Limitations of the current ATLAS
Previous generation ECR Low Energy Beam Transport Multi-Harmonic Buncher
– Low voltage, strong space charge effects
– As a result not efficient for high current beams (>10 pA)
Low transverse acceptance of the first PII cryostat– The aperture diameter of the first cavity is 15 mm, the second cavity – 19 mm
– The transverse acceptance is ~0.6 mm-mrad, normalized
– Strong transverse-longitudinal coupling in the first cavities at high field – emittance growth
Longitudinal emittance growth – Non-adiabatic motion in the phase space, low acceptance, emittance growth for
high-intensity beams and beam losses
Beam steering in the split-ring cavities, especially for light ions RF system was not designed to compensate beam loading Cryogenics, Radiation Shielding, Control system, Beam diagnostics,….
5P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
CARIBU
Tandem New cryomodule
Current ATLAS Layout
6P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Feasible solutions
ECR: Upgrade existing ECR EBIS: Increase efficiency of CARIBU beams by factor of 2 and higher Low Energy Beam Transport: Re-design, more frequent focusing,
possibly electrostatic Multi-Harmonic Buncher
– Increase voltage (water cooling), move closer to the RF accelerator
Low transverse acceptance of the first PII cryostat– Replace with the normal conducting RFQ accelerator
Longitudinal emittance growth due to high accelerating fields– Adiabatic acceleration in the RFQ up to ~250 keV/u, no emittance growth
Beam steering: Replace two Booster cryostats with new cryostat with 6 or 7 /4 cavities
RF system was not designed to compensate beam loading: New couplers, new RF system
Cryogenics, Shielding, Controls, Diagnostics,….Upgrade
7P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Beam time structure and intensities
Maintain 12.125 MHz beam time structure – 80 ns between bunches
In the following discussions:
Low intensity ion beams (CARIBU) ≤ 0.1 pAMedium intensity ion beams ~1.0 pA (current ATLAS performance)High intensity ion beams ~10 pA
8P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
CARIBU
Gas cell + Mass Separator
EBIS
MHB RFQ MEBT 2 new cryomodules Energy upgrade cryomodule
ATLAS High-Intensity Upgrade, PHASE II (Total $45M)
1) 14 QWR, G=0.075, f=72.75 MHz2) EBIS charge breeder3) Upgraded ECR4) Gas cell and Mass Separator
2 Booster and 2 ATLAS cryomodules
Available space for future experiments
9P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Phase I: Beam energies as function of Q/A
Q/A High Intensity Energy (MeV/u)
Low Intensity Energy (MeV/u)
1/1 14.2 34.5
1/2 8.8 21.4
1/3 6.7 16.0
1/4 5.4 12.9
1/5 4.6 10.8
1/6 4.0 9.3
1/7 3.6 8.1
Note: High intensity energy is before the booster Low intensity energy is the full energy
2 PII Cryo. 12 cavities (existing) 1 New Cryo. 6 QWR @ 72.75 MHz for β ~ 0.075 (new) 3 Booster Cryo. 16 cavities (existing) 2 ATLAS Cryo. 12 cavities (existing) 1 Upgrade Cryo. 7 QWR @ 109.125 MHz for β ~ 0.15 (existing)
10P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Phase I: Example Beams
Z A Q High Intensity Energy (MeV/u)
Low Intensity Energy (MeV/u)
8 16 6 7.2 17.5
18 40 12 6.2 14.8
36 84 25 6.1 14.7
54 136 28 4.7 11.1
92 238 34 3.6 8.1
Note: High intensity energy is before the booster Low intensity energy is the full energy
11P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
2 PII 1 New 3 Booster 2 ATLAS 1 Upgrade
Phase I: Q/A = 1/7 - Cavity Voltage Profile
P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Phase II
2 PII Cryo. 12 cavities (existing)
2 New Cryo. 14 QWR @ 72.75 MHz for β ~ 0.075 (new)
2 Booster Cryo. 12 cavities (existing)
2 ATLAS Cryo. 12 cavities (existing)
1 Upgrade Cryo. 7 QWR @ 109.125 MHz for β ~ 0.15 (existing)
Q/A High Intensity Energy (MeV/u)
Low Intensity Energy (MeV/u)
1/1 25.2 41.7
1/2 15.5 25.9
1/3 11.6 19.5
1/4 9.4 15.8
1/5 8.0 13.3
1/6 6.9 11.6
1/7 6.1 10.2
Note: High intensity energy is before the booster Low intensity energy is the full energy
13P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Phase II: Example Beams
Z A Q High Intensity Energy (MeV/u)
Low Intensity Energy (MeV/u)
8 16 6 12.7 21.2
18 40 12 10.8 18.0
36 84 25 10.7 17.9
54 136 28 8.2 13.6
92 238 34 6.1 10.2
Note: High intensity energy is before the booster Low intensity energy is the full energy
14P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
ATLAS Efficiency and Intensity Upgrade schedule (PHASE II)Development,
Activity installation (Year) Comments
1 New Charge Breeder based on Electron Beam Ion Source 2010-2013
2 R&D, resonator development, RFQ construction 2009- 2012 Phase I, funded
2 Infrastructure improvements 2010-2013Cryogenic distribution 2010-2011 Phase I, partiallyImprovements of the SRF Facility 2010 fundedBuilding modifications 2013Decommissioning of the Tandem 2013
3 Front end systems: LEBT, MHB 2010-2011
4 ATLAS improvements for higher intensity beams 2009-2013ECR 2011Focusing system, RF system, Diagnostics and Controls 2011-2013Administration, Safety 2009-2013
5 New cryomodule fully populated with 2010- 2012resonators, couplers, tuners, βG=0.075
6 One more cryomodule fully populated with 2011- 2013resonators, couplers, tuners, βG=0.075
7 New experimental equipment 2013New CARIBU Source Transfer Facility 2013In-flight Beam Separator 2013
Phase I, funded
15P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
CARIBU
MHB RFQ MEBT New cryomodule Energy upgrade cryomodule
ATLAS High-Intensity Upgrade: PHASE I (ARRA)
1) Modify PII-1, install RFQ2) G=0.075, f=72.75 MHz – one cryomodule3) LHe system upgrade
16P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
PHASE I – ARRA
Build new RFQ to boost beam energy to ~250 keV/u for q/A=1/7– 80% efficiency of bunching and acceleration, upgrade MHB
– Capable to accelerate 1 mA beams
Build a new cryomodule with ~6 SC cavities, G =0.075
– Capable to accelerate 1 mA beams
– New high-power coupler
– Based on design of the Energy Upgrade Cryomodule
Modify the first cryomodule of the PII Remove the first 2 cryomodules of the Booster (G=0.06 cavities)
Upgrade LHe distribution system: higher efficiency and reliability
17P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Multi-Harmonic Buncher, 58Ni15+ , 35.7 keV/u
ATLAS: 10 meters between the MHB and the RF LinacAfter the MHB Low current (<1 pA) 0.5 mA
MHB - RF Linac
distance is 3.5 m
18P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
1/7≤q/A≤ 1 Injection energy = 30 keV/u 60.625 MHz, 5th harmonic,
~3.0-meter length 80% efficiency of beam capture
for acceleration Voltage ~90 kV, R0=7.5 mm
High-temperature furnace brazing ~100 kW RF power 2 circuits of temperature-stabilized
water-cooling systems
RFQ
19P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
60.625 MHz RFQ will be very similar to the FRIB prototype
Pre-brazed assembly Prototype RFQ
Stable operation in wide dynamic range of RF power
– The highest voltage is 91 kV (limited by available RF power) Q-factor: Simulation = 9300, Measured = 8860 3-meter long RFQ will provide ~250 keV/u ion beams, Q/A1/7
Fabrication technology:High-T furnace brazing, OFE copper
20P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
80.65% captured to the central bunch
21P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
ARRA: new cryomodule with QWR @ 72.75 MHz, βG=0.075
Electromagnetic optimization is complete
Reduced BPEAK/EACC
Reduced EPEAK/EACC
Expected performance– VMAX= 2.5 MV
– BPEAK = 600 Gs
– EPEAK = 45 MV/m
About 50% better performance
than the ATLAS Upgrade
Cryomodule
25 cm109.8 cm
3 cm
14 cm
22P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Couplers
Existing ATLAS couplers (≤ 1 kW)
Proposed high-power (~10 kW) capacitive coupler
23P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Tuners
AEU pneumatic slow tuner:
excellent performance
Replace VCX with piezoelectric tuner– Can handle higher accelerating gradients
Piezoelectric fast tuner,tested on spoke cavities
0
2
4
6
8
10
12
14
16
EA
CC (
MV
/m)
R331 R332 R333 R334 R335 R336 R337
Without VCXOperational
24P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Current activities on new ARRA-RFQ project Project documentation
– WBS
– Schedule – off-line commissioning in June 2012
– Implementation Plan
Study of the transmission of high-intensity beams through the PII, beam steering, transverse acceptance.
Design optimization of the accelerator – LEBT, RFQ, matching to the PII cryostat
RFQ prototype– Modify RF coupler with additional cooling and test
– Build slug tuners, install and test
EM simulations of the RFQ resonator– Accurate frequency calculation
– Minimize length and RF power
25P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Frequency verification: Simulations vs Experiment
26P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
RFQ
Test high-power coupler (~120 kW) with an additional cooling Build and test slug tuners
27P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Current activities on new ARRA: Booster replacement project
Develop and prototype QWR, f=72.75 MHz cavity. The following features will be implemented:– Highly optimized EM design
– SC cavities with “beam steering compensation”
– New approach for electropolishing of QWRs
– Develop and test adjustable (1-1/2”) capacitive coupler to handle ~10 kW RF power.
– Develop piezoelectric tuner
Apply the vast experience gained during the ATLAS Energy Upgrade cryomodule
28P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
ATLAS Energy Upgrade Cryomodule
29P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
ATLAS Energy Upgrade Cavities are ready to drop into the box cryostat
30P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
New coupler
(cm)
Double window: cold and warm
31P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Prototyping
Fast piezoelectric tuner Capacitive coupler Use the existing half-wave resonator
and new test cryostat
32P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
60 MHz 20 kW CW amplifier is available both for the test of the RFQ segments and can be retuned to 72 MHz for conditioning of SC QWRs
Was purchased for testing of the prototype RFQ
33P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Charge Breeder based on EBIS for CARIBU beams
Low intensity of CARIBU beams allows us to efficiently apply EBIS for charge breeding. Compared to ECR:– Factor of 2-3 higher efficiency
– Significantly higher purity
EBIS parameters are less demanding than the BNL EBIS Major challenges are
– precise alignment of electron and ion beam required
– achieve high acceptance and short breeding times
B EBIS LEBTFrom CARIBU
Mass-Separator
To ATLAS
Post- Accelerator1+ (2+)Q+
Q/A1/7A=80-160
B: RFQ Buncher
EBIS: Electron Beam
Ion Source
LEBT: Low Energy Beam
Transport
EBIS charge breeder design is based on BNL Test-EBIS: Double e-gun approach: 2A/5 kV and 0.2A/2 kVElectron beam current density – 300 A/cm2 (BNL – 575 A/cm2) Breeding time – 30 – 40 ms Efficiency ~ 15%, can be higher by factor of 2-3 when shell closure effect is applicable
34P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
EBIS R&D for the CARIBU beams
In collaboration with BNL– Build low-emittance 1+ injector, beam diagnostics for breeding efficiency
measurements for low-intensity beams
– Study shell closure effects at the BNL test-EBIS. For this purpose ANL will build low-current, high-perveance electron gun
35P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Summary of upgraded ATLAS ion beams and future activities (no stripping is assumed)
PHASE I PHASE II
Energies of high intensity beams (~10 pA)
5.4 MeV/u (1/4 ≤ Q/A)
to 9 MeV/u
6.1 MeV/u (1/7 ≤ Q/A)
16 MeV/u
Energies of low intensity beams (~1 pA)
8.1 – 21.4 MeV/u 10.2 - 26 MeV/u
Transmission efficiency of CARIBU beams
80% 80%
Major upgrades 1) New CW RFQ
2) A new cryomodule of beta=0.075 QWR
3) Improve LHe distribution system
1) Upgraded ECR for stable beams, higher intensities
2) EBIS charge breeder
3) One more cryomodule of beta=0.075 QWR
4) Relocated SRF, upgrade of ATLAS sub-systems
5) New experimental equipment
36P.N. Ostroumov ATLAS Efficiency & intensity upgrade August 8-9, 2009
Conclusion
The Physics Division has developed detailed plan for future ATLAS upgrade – PHASE I – two ARRA projects
– ARRA-funded ATLAS upgrade is based on R&D results performed for FRIB, ATLAS AIP
– We are in the stage of preliminary design for both ARRA projects
Schedule:– Commissioning of the RFQ – efficiency upgrade – September 2012
– Commissioning of the Booster replacement cryomodule – high-intensity medium mass beams – December 2012.
PHASE II is not funded yet, can be completed by the end of 2013 if the funds become available in FY10.
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