Measurement of the SEISM (Sixty GHz ECR Ion Source using Megawatt Magnets)
magnetic field map
Mélanie MARIE-JEANNE
J. Jacob, T. Lamy, L. Latrasse from LPSC Grenoble
F. Debray, J. Matera, R. Pfister, C. Trophime from LNCMI Grenoble
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 2/18
Outline
• Why a 60GHz prototype ?
• Results of the design study
• Technical challenges of fabrication
• Magnetic field measurements
• What next ?
Why a 60GHz prototype ? (1)
For the beta-beam project
Multi-ionizing and bunching radioactive gases diffusing from the target
Neutrino beams
Ion production
6He, 18Ne storage and β- decay
RADIATION RESISTANTHIGH CURRENTS
Close to target 1013 at/s yields
EFFICIENT IONIZATION SHORT CONFINEMENT TIME
Short half-lives from 807ms (6He) to 1.67s (18Ne)
PULSED MODESHORT BUNCHES
10Hz to 25Hz duty cycle50-100μs pulses
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 3/18
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 4/18
Experimental Ar4+ preglow pulse from PHOENIX V2 at 28GHz
Izotov I.V., Lamy T., Latrasse L., Sidorov
A.V., Skalyga V.A. et al IEEE Transactions
on Plasma Science 36/4 (2008) 1494-1501
PREGLOW MODE
Polyhelix technology developed at LNCMI Grenoble
New ECR magnetic structures
using resistive polyhelix coils
60GHz high density plasma
RADIATION RESISTANT
Compact (combined to target)
Why a 60GHz prototype ? (2)
What kind of prototype
60GHz ECRIS
SHORT BUNCHES
HIGH CURRENTS
Preglow mode
PULSED MODE
SHORT CONFINEMENT TIME
Origins of 60GHz project: presentation by P. Sortais in Moriond - Les Arcs, March 17-22, 2003
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 5/18
Results of the design study (1)
L. Latrasse et al., SEISM: A 60 GHz cusp electron cyclotron resonance ion source, Rev. Sci. Instrum. 81, 02A324, 2010
Compact CUSP magnetic structure
4 T
3 T6 T
4 T
Injection Extraction
2.1 T
Field line
60
mm
Peak to peak ~100 mm
ECR zone
4 T
3 T6 T
4 T
Injection Extraction
2.1 T
Field line
60
mm
Peak to peak ~100 mm
ECR zone
injection
extraction
Plasma chamber
Magnetic field above expectations
6.9 T
4.9 T
4.9 T
3.5 T
SEISM prototype
H1 aluminum prototype
0
50
100
150
200
250
300
350
400
-150 -100 -50 0 50 100 150 200
z (mm)
B s
ur
l'a
xe
(G
au
ss
) Expérience
Calcul
H4
H4
H2
H2
H1
H1
H3
H3
2 current leads per coil
bossage to avoid rotation
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 6/18
Results of the design study (1)
SEISM prototype
30kA current on each set of coils
Fake plasma chamber
Stainless steel rod
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 7/18
Results of the design study (1)
SEISM prototype
28l/s waterflow in each tank
Water inlet
Water outlets
Water inWater out
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 8/18
Valve
Flowmeter
Deionized
water inlet
Flexible pipes
Deionized
water outlet
Flexible power cables
Magnetic measurement
systems
Flexible power
cables
On-site connection to a running magnet for half-magnetic field test
Electric parameters
I = 15000 A
P = 0.75 MW (one coil set)
Cooling parameters
Q = 22 l/s
Pin = 20 bars
Max coil temperature
Tmean = 50 °C
TMax. loc. 70 °C.
Results of the design study (2)
Voltagemeasurement
Jack
Hall probe
Visit LNCMI on Thursday !
•Electrically in series
•Hydraulics in parallel
Test bench at LNCMI Grenoble
13T – 10MW magnet2x13000A applied
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 9/18
Technical challenges (1)Insulating between the helices windings
• Narrow insulators (2mm wide) to minimize local heating• Height calibration (0.32mm height)• 24 sectors on inner coil, 32 sectors on outer coil to avoid
contact between the windingsTemperature calculations
Winding displacement calculations
insulators Height calibrating pieces
Heating tests on prepreg
Damaged resin
« prepreg » for pre-impregnated composite fibres
G11 dry woven glass fabric impregnated with epoxy resinSpecified maximum continuous operating temperature: 165°C
Specified breakdown voltage condition: 35kV/mm
Out of stock ! Tests with frozen out-of-date prepreg20MPa at room temperature
Resin damaged for local temperatures around 300°C
0
5
10
15
20
0 2000 4000 6000 8000 10000 12000 14000
Wate
r fl
ow
(l/s)
Current (A)
Water flow vs applied current
Injection tank
Extraction tank
Injection tank with porous disks
Extraction tank with porous disks
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 10/18
Technical challenges (2)Hydraulic circulation from the inner to the outer coil
• Tests with fake aluminum helices
water circulation up to 18bars – 18l/s in each tank
cavitation noises, small damage marks on aluminum
• Tests with copper helices and measurements up to 7000A
10bar - 12l/s in each tank _ water speed up to 14m/s in the radial helices slit
cavitation noises
• Porous discs to slow down the flow in SEISM, but not in the LNCMI magnet running in parallel
no more cavitation, but a filter damaged after 24 hours of run28l/s waterflow in each
tank
∆P ~ 0.5 bar in the helices
19.5 bar on the porous disc
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 11/18
Voltage measurement to monitor the coils resistance / temperature:
Technical challenges (3)Temperature monitoring
insulators
Snapshot of the outer coil insulators after 40 hours of run up to 7000AInserting a camera to have a look:
++ insulators still aligned !
-- color indicates local temperature is higher than expected
Voltagemeasurement
Mean temperature evolution
0
5
10
15
20
25
30
35
40
2000 4000 6000 8000 10000 12000 14000 16000
Current (A)
Delt
a T
injection
extraction
injection with poral discs
extraction with poral discs
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 12/18
Jack
Hall probe
Controllers
• 300mm-course jacks with a step-by-step motorequipped with a probe holder
Magnetic field measurements (1)Measurement setup
• Measurement on 3 horizontal axes along z and on one radial axis
4 T
3 T6 T
4 T
Injection Extraction
2.1 T
Field line
60
mm
Peak to peak ~100 mm
ECR zone
4 T
3 T6 T
4 T
Injection Extraction
2.1 T
Field line
60
mm
Peak to peak ~100 mm
ECR zone
30mm15mm0mm
Axial field in LNCMI M5 magnet
0
1
2
3
4
5
6
7
0 2000 4000 6000 8000
Current intensity (A)
Axia
l fie
ld B
z (
T)
Bell615 Hall probe
M5 magnet calibration
curve
Axial field in LNCMI M5 magnet
0
0,5
1
1,5
2
2,5
3
3,5
4
0 1000 2000 3000 4000
Current intensity (A)
Axia
l fie
ld B
z (
T)
Bell5080 Hall probe
M5 magnet calibration
curve
• Two gaussmeters equipped with single-axis axial and radial Hall probes
• LabView interface to move jacks and acquire data
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 13/18
As expected:Radial field measurement on axis 15mm at 3500A
-0,2
-0,1
0
0,1
0,2
0,3
-250 -200 -150 -100 -50 0 50 100 150
z (mm)
Br x
-com
pon
en
t (T)
probe HORIZONTAL at angle 90deg
probe VERTICAL at angle 0deg
Magnetic field measurements (2)Preliminary results vs simulations
Axisymmetric field
Increase with distance to central axis
Scaling with increase of the intensity
Unexpected: Shift in maxima positions
Lower amplitude on extraction side
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
3
-200 -100 0 100 200
Bz (
T)
z (mm)
Axial magnetic field on central axis
1500A
3500A
5250A
7000A
8750A
10500A
-3
-2
-1
0
1
2
3
4
-200 -100 0 100 200
Bz (
T)
z (mm)
Axial magnetic field on central axis
1500A
3500A
5250A
7000A
8750A
10500A
14000A (extrapolated)
14000A (calculations)
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 14/18
Magnetic field measurements (2)Preliminary results vs simulations
Axial field on central axis at 7000A
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
-200 -150 -100 -50 0 50 100 150 200
z (mm)
Bz (
T)
simulation-injection
simulation-extraction
simulated sum
Axial field on central axis at 7000A
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
-200 -150 -100 -50 0 50 100 150 200
z (mm)
Bz (
T)
simulation-injection
simulation-extraction
measurement-injection
measurement-extraction
Axial field on central axis at 7000A
-1,5
-1
-0,5
0
0,5
1
1,5
2
2,5
-200 -150 -100 -50 0 50 100 150 200
z (mm)
Bz (
T)
simulation-injection
simulation-extraction
measurement-injection
measurement-extraction
simulated sum
sum of measurements
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 15/18
• Mechanical error (tank dimensions, helix positioning)Injection and extraction coil sets are too closeSum of the amplitudes is modified Not likely to cause 10mm difference, tanks dimensions were checked and within tolerances
Magnetic field measurements (3)Possible explanations
• Misplaced magnetic center because helix shape is wrongElectric discharge machining with a 0.25mm wire
For example real split is 0.37mm instead of expected 0.32mm
Magnetic centers can be checked individually for each helix after dismounting
• Calculation errorConsidered heat transfer is wrong
Copper resistance is higher, current density is lower, and resulting magnetic field is lower
Comparative simulations should be performed
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 16/18
Conclusion
• The SEISM magnetic structure was built and set up on a test bench at LNCMI Grenoble
• Continuous magnetic field has been produced on-site for 70h up to now
• Results show an axi-symmetric field map with a lower amplitude and closer maxima than expected from the simulations
• Possible explanations involve mechanical errors in the fabrication of the polyhelix coils or the water tanks, and are still under investigation
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 17/18
What next ?
• Right now: Damaged poral disc to be replaced Gaussmeter with triple-axis Hall probe to be bought Magnetic field measurements up to 14000A (2 weeks run to be scheduled in automn 2010)
• Next year: Plasma chamber design permanent room at LNCMI is under funding request for first tests at 28 GHz
• In a near future: Preparation to raise the current to full intensity (30kA)
Adding direct voltage reading on each individual helix Adding temperature reading on local non-cooled parts (insulators) Insulators replacement ? What kind ?
60 GHz gyrotron is currently under construction at IAP-NN (ISTC contract)
August 28, 2010 Mélanie MARIE-JEANNE ECRIS’10 - Grenoble, France 18/18
Acknowledgements
To numerous people from the SERM-LPSC workshop
To the LNCMI Magnet Group