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1. Introduction
2. High intensity proton beam measurements at GSI-UNILAC
3. Pushing the limits for uranium beam operation
4. Heavy ion stripping
5. beam brilliance analysis
6. U28+-beam brilliance at SIS18 injection
7. Summary&Outlook
High Current Uranium Beam Measurements at GSI-UNILAC for FAIR Winfried Barth, GSI&HIM A. Adonin2, Ch. E. Düllmann1,2,3, M. Heilmann2, R.Hollinger2, E. Jäger2, O. Kester2, J.Khuyagbaatar1,2, J. Krier2, E. Plechov2, P. Scharrer1,2,3, W.Vinzenz2, H. Vormann2, A.Yakushev1,2, S. Yaramyshev2
1 Helmholtz Institute Mainz, Germany 2 GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany 3 Johannes Gutenberg-Universität Mainz, Germany
1. Introduction The GSI UNIversal Linear ACcelerator
High Current Injector (1999) Alvarez (1975) Single Gap Resonators (1975)
High Charge State Injector (1991)
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR 2
3
Facility for Antiproton and IonResearch
Upgraded existing facility:´ion-beam source and injector for FAIR
Primary beams: protons to 238U
Accelerator Components & Key Characteristics
Ring/Device Beam Energy Intensity SIS 100 (100Tm) protons 30 GeV 4x1013
238U 1 GeV/u 5x1011 (intensity factor 100 over present)
SIS 300 (300Tm) 40Ar 45 GeV/u 2x109
238U 34 GeV/u 2x1010
CR/RESR/NESR ion and antiproton storage and experiment rings HESR antiprotons 14 GeV ~1011
Super-FRS rare isotope beams 1 GeV/u <109
New future facility: ion and anti-matter beams of highest intensities and high energies
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
LEBT RFQ HSI Gasstripper Alvarez Single GapRes.
TK Emittance@TK
Ion
cu
rren
t [m
A]
April 14
May 14
July 14
October 14
October 15
p+ - design limit
H3+ (3)p+
CH3+ (3)p+
C3H7+ (7)p+
2. High intensity proton beam measurements at GSI-UNILAC
4 W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Front to end emittance measurements with a high current proton beam
5
W. Barth, et al., Phys. Rev. ST Accel. & Beams 18, 050102 (2015)
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
High Current Proton Beam Analysis
6
Analysis of (horizontal) beam emittance
Horizontal multi-turn injection into SIS18 • Beams are stacked until machine
acceptance is reached • Loss should be as low as possible
due to activation, damage, vacuum
... fixed particle number ... fixed relative fraction
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
3. Pushing the limits for uranium beam operation
7
• Ion Source: Applying a multi-aperture extraction system at the VARIS ion source Increased U4+-intensity and improved primary beam brilliance
• Low Energy Beam Transport: Improved LEBT-performance and RFQ-Matching using high brilliance uranium beam from the VARIS 70% RFQ-Transmission (Iout = 9.7 emA)
• RFQ: RF optimization by adjusting plunger positions at the HSI RFQ tank and extensive rf-conditioning Reduction of forwarded rf-power, yielding for reliable high-current uranium beam operation.
• MEBT: Optimizing the between RFQ and IH DTL by increasing the transverse and longitudinal focusing strength (3%) Reduction of beam loss, stable high current operation
• 1.4 MeV/u-Transport Line: Adapting the quadrupole channel (matching the gas stripper) 90% beam transmission, U4+ beam current of 6.6emA available for heavy ion stripping.
High Current Injector
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
4. Heavy Ion Stripping
• For high intensive heavy ion beams Increase of the so called „ionic charge“ by collision with matter (= STRIPPING, Removal of electrons) Reduction of the necessary effective potential for the acceleration of ions.
• Collision of heavy ions with matter e—capture ( Z5) and e--loss ( Z4)
• (Pulsed) H2 gas stripping cell with target thickness > 10μg/cm2
gas stripper section
-10 0 +10 X [mm]
-10
0
+10
Y [m
m]
27+ 28+ 29+
238U
8 W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
N2
H2
Particle Stripping Efficiency
U26+ U29+
N2-gas jet [6] H2- gas cell
Stripper-back-pressure 0.4 MPa 5.5 MPa (pulsed)
U4+-current (HSI) 6.0 emA 6.6 emA
Stripping charge state 28+ 29+
Max.uranium-current 4.5 emA 9.97 emA
Stripping efficiency 12.70.5% 21.00.8%
Energy loss 145 keV/u 275 keV/u
x (90%, tot.) norm. 0.76 µm 0.66 µm
y (90%, tot.) norm. 0.84 µm 1.15 µm
Hor. brilliance (90%) 5.32 mA/µm 13.60 mA/µm
Beam Energy Loss:
U28+ N2-jet (max.) 145 keV/u
U28+ Pulsed H2-stripper cell (1 valve, 7.5 MPa) 175 keV/u
U29+ Pulsed H2-stripper cell (2 valves, 5.5 MPa) 27 5 keV/u
Beam Parameters:
9 W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
10
0
4
8
12
16
LEBT HSI gas stripper
ion
curr
ent
[em
A]
Oct 14
Nov 14
Oct 15
Design
U4+
U28+
High Current Uranium Beam Transmission
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
High Current Uranium Beam Measurements at 1.4 MeV/u
horizontal vertical
-20 0 20 X [mm]
15
0
-15
X‘ [
mra
d]
-20 0 20 Y [mm]
15
0
-15
Y‘ [
mra
d]
-20 0 20 X [mm]
15
0
-15
X‘ [
mra
d]
-20 0 20 Y [mm]
15
0
-15
Y‘ [
mra
d]
H2 H2
N2 N2
norm.,tot,99% = 1.8 mmmrad norm.,tot,99% = 1.1 mmmrad
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Beam Profile Measurements at 1.4 MeV/u
12
Beam spot (charge separation):
Pure separation from neighbouring charge states
emittance growth (momentum straggling) spot size
Ana
lyzi
ng s
lit
High Current Injector
Poststripper
Stripper box
QD 1 QD 2 QT
QD 3
D 1
D 2
D 3
Analyzing slit
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
13
5. Beam Brilliance Analysis
0
10
20
30
40
0 2 4 6 8 10
Bea
m B
rillia
nce
[mA/m
m]
I [emA]
238U28+
I = 9.7 emA @1.4 MeV/u
Bx [mA/muem]
By [mA/muem]
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
High brilliance uranium beam measure-ments at 1.4 MeV/u
0.0
0.3
0.6
0.9
1.2
0 20 40 60 80 100
Hor
. Bea
m E
mitt
ance
[m
m]
Fraction [%]
238U28+
N2-Target, 4.5 emA
H2-Target, 7.8 emA
H2-Target, 9.7 emA
Gain of intensity:
Increased particle number inside same hor. emittance
higher beam brilliance 0.0
0.3
0.6
0.9
1.2
0 2 4 6 8 10
Hor
. Bea
m E
mitt
ance
[m
m]
I [emA]
238U28+
0.45 mm ... fixed particle number
... fixed relative fraction
General analysis of fraction emittance
X [mm]
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
15
0
10
20
30
40
0 2 4 6 8 10
Hor
. Bea
m B
rillia
nce
[mA/m
m]
I [emA]
238U28+ 4.0 emA5.0 emA7.8 emA9.7 emA
Horizontal Beam Brilliance Analysis
Fractional Beam Brilliance for I = 3 emA
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
5
10
15
20
25
30
35
40
3 5 7 9 11
Bx [
mA/
µm]
IU28+ [emA]
k 4.3
I = 1 emA Bx = 4.3 [mA/mm] (for a fractional current of 3 emA)
16
Fractional Beam Brilliance for a fixed Particle Number I = 3 emA
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Emittance Beam Analysis
17
Proton beam emittance
0.0
0.4
0.8
0 5 10 15
Hor
. Bea
m E
mitt
ance
[m
m]
I [emA]
238U28+
17 emA (rescaled, 2 mA, p)9.7 emA7.8 emA4.5 emA
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Uranium beam emittance
6. U28+-beam brilliance at SIS18 injection
• Determination of U28+-beam brilliance at SIS18 injection: High current U28+-beam brilliance measurement at 1.4 MeV/u Front-to-end high-current proton beam measurements (up to 11.4 MeV/u)
• UNILAC parameters scale with the mass-to-charge ratio m/q:
• Proton beam transmission TMfin (stripper until) SIS18-injection:
• Proton rms emittance growth EWfin(p+); considering particle loss:
• Resulting proton beam brilliance loss BL(p+):
• Assuming brilliance loss scales with ion current density brilliance loss BL(U28+) for the measured maximum uranium beam current (for charge state 28+) of 9.70emA:
18
15.8
)(
)()(
28
pqm
Uqm
scalqm
%75)( pTM fin
%3)( pEW fin
%23%100)(%100
)(%100)(
pEWpTM
pBLfin
fin
%.15%236.0)()(2
70.9)( 28
pBLscal
qmemA
emAUBL
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Loss free (high current) U28+-beam injection into the GSI-synchrotron SIS18
19
• UNILAC beam measurement at 1.4 MeV/u • Reduced UNILAC beam brilliance at SIS18 injection • SIS18-beam intensity to achieve space charge limit (2•1011 part. per pulse) • SIS18-beam intensity after multi turn injection (𝑰𝒔𝒄𝒍 = 𝟏𝟖𝟕. 𝟓 𝒆𝒎𝑨)
30 turn injection
S. Appel, private communication (2016) 0
50
100
150
200
0
4
8
12
16
0 0.5 1 1.5 2 2.5 3 3.5
ISIS18 [emA]
I 0 [m
A]
hor. emittance [mm mrad]
measured (1.4 MeV/u)
UNILAC (11.4 MeV/u)
SIS18-injection
ISIS18 [emA]
𝑰𝒔𝒄𝒍 = 𝟏𝟖𝟕. 𝟓 𝒆𝒎𝑨
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
7. Summary and Outlook
20
Loss-free injection into the SIS18 is a necessary condition, especially for operation with high intensity heavy ion beams.
By horizontal collimation of the UNILAC beam emittance in the transfer line, the SIS18 space charge limit could be reached at significantly lower peak currents, but accordingly longer injection times (55 µs 138 µs)
The conducted high current proton beam emittance measurement throughout the UNILAC shows a loss of horizontal beam brilliance of 23% the high current uranium beam brilliance (measured at 1.4MeV/u) grows until SIS18 injection accordingly.
The horizontal beam brilliance growths strongly with the beam intensity
For higher currents the core of the uranium phase space distribution perhaps remains constant during acceleration and beam transport
30 turns have to be injected in the SIS18 to fill up to the SCL (Design: 12 turns; Iunilac = 15 emA)
For further confirmation, it is evident to perform uranium measurements at full UNILAC energy.
Through horizontal collimation (2mmmrad), the number of measured uranium particles in this phase space area could be sufficient to fill the SIS18 up to the space charge limit (2•1011 part. per pulse).
W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR
Thank You for Your Attention!
21 W. Barth, High Current Uranium Beam Measurements at GSI-UNILAC for FAIR