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30 GHz r esults from 2008. Mathias Gerbaux CTF3 Collaboration Technical meeting 27/01/2009. F. D. F. F. D. D. F. F. D. D. F. F. F. F. D. D. F. F. F. F. F. F. D. D. F. D. D. D. D. D. F. F. D. D. D. D. F. F. D. D. F. F. D. D. F. F. D. D. D. F. F. - PowerPoint PPT Presentation
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Mathias Gerbaux
CTF3 Collaboration Technical meeting27/01/2009
30 GHz results from 2008
CTF3 Collaboration meeting Jan 2009 G.Geschonke
2
DL2006/7
Thermionic gun
CR
30 GHz production (PETS line)and test stand
Linac
D FFD
DF
F
D F D
D F D D F D
D F D
DF DF DF DF DF DF DF DF DF
D F D
F DF D
D FFFDD
DF
FDD
FF
FF
D F DD F D
D F DD F D D F DD F D
D F DD F D
DF DF DF DF DF DF DF DF DF DFDF DF DF DF DF DF DF DF DF DF DF DF DF DF DF DF
D F DD F D
F DF DF DF D
CTF2CLEX
To set the stage…
3
Structures tested in 2008
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
Only two…
• HDS4_thick : re-test, bad results. Didn’t reach an accelerating gradient much higher than 60 MV.m-1.
• C30 speed bump : same geometry as the older 3.5 mm structure except for a « speed bump » lowering the group velocity at the input. Two measurements : fed by the input and by output.
4
Speed bump (TM03)
R=14.398 mm
R_iris= 2.428 mm
Iris_thickness= 1mm
Bandwidth
-10
-9
-8
-7
-6
-5
-4
-3
-2
-1
0
29.5 29.6 29.7 29.8 29.9 30 30.1 30.2 30.3 30.4 30.5
f (GHz)
S12
(dB
) Speed bump TM03Speed bump TM02Original
0
0.01
0.02
0.03
0.04
0.05
0.06
0 1 2 3 4 5
cell #
vg/c
2nd mode speed bumpregular cell nominal value3rd mode speed bump3rd mode,final version
Test structure in disks: 30 cell and identical mode launcher of the “conventional” 2π/3 Ø 3.5 mm
Courtesy of
Riccardo Zennaro
5
0 100 200 300 400 500 600 700 800 9000
20
40
60
80
100
120
Time (h)
Acc
eler
atin
g gr
adie
nt
0 100 200 300 400 500 600 700 800 9000
20
40
60
80
100
120
Time (h)
Puls
e le
ngth
@ 50%@ 75%
HDS4_thick re-test: whole history
In total : 1,244,800 pulses, mainly at 1 Hz corresponding
to 5.76 SLAC hours at 60 Hz but crappy data
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
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208 208.2 208.4 208.6 208.8 209 209.2 209.4 209.6 209.8 2100
10
20
30
40
50
60
70
80
Time (h)
Acc
eler
atin
g gr
adie
nt
208 208.2 208.4 208.6 208.8 209 209.2 209.4 209.6 209.8 2100
20
40
60
80
100
120
Time (h)
Puls
e le
ngth
@ 50%@ 75%
HDS4_thick re-test : typical running
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
7
0 1 2 3 4 5 6 7 8x 10
4
0
500
1000
1500
2000
2500
Pulse number
Ener
gy
IncTransRefl
C30-sb
In total : • 4,101,250 pulses, mainly at 1 Hz
corresponding to 18.99 SLAC hours at 60 Hz• 2186 breakdowns
Weird things due to calibration problems (now solved)
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
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0 0.5 1 1.5 2 2.5 3 3.5x 10
4
0
500
1000
1500
2000
2500
3000
Pulse number
Ener
gy (m
J)
IncTransRefl
1 point every 50 pulses
C30-sb-reversed
In total : • 1,704,650 pulses, mainly at 1 Hz
corresponding to 7.89 SLAC hours at 60 Hz• 501 breakdowns
Weird things due to calibration problems(now solved)
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
9
We figured out at the end of Fall 2008 that calibration was affected by various factors (drifting baselines, temperature…).
If we assume the measurement of the incident power is not too wrong…
Or at least it is only the absolute calibration that is wrong and it don’t change too quickly.
Then, we can calculate the breakdown rate as a function of the accelerating gradient .
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
10
1606 1608 1610 1612 1614 1616 1618 1620 1622 1624 162630
40
50
60
70
80
90
100
Time (h)
Acc
eler
atin
g gr
adie
nt
1606 1608 1610 1612 1614 1616 1618 1620 1622 1624 1626
20
40
60
80
100
Time (h)
Puls
e le
ngth
@ 50%@ 75%
OK
Breakdown rate calculation
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
Breakdown rate vs gradient – speed bump structure
65 70 75 80 85 90 95 100
10-6
10-5
10-4
10-3
10-2
Peak gradient (MV/m)
Bre
akdo
wn
rate
C30-sbUpper limits
-- Old 3.5mm structure
3.5 mm structures comparison
• No effect of the speed bump on the breakdown rate
• Need post-mortem examination to see if it has one on the surface damage
• Vertical error bars calculated assuming an error of 1 on the breakdown number and 500 on the number of pulses.
• Horizontal error bars : standard deviation of the measured gradient.
• Red circles are upper limits (no breakdown recorded).
• Fit doesn’t take into account these points.
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
12
DIY electron spectrometer
RLRL
lLdXarcsintan1
arcsintan)(
Rough calculations :•with B=0.15 mT (0.1 A), E(e-) > 200 eV •with B=0.75 mT (0.5 A), E(e-) > 10 keV •with B=3.0 mT (2.0 A), E(e-) > 200 keV•with B=7.5 mT (5.0 A), E(e-) > 500 keVα
α
B
R
L
lXd
CCD
45°
Speed bumpstructure
magnet
Alumina screen
0 A 0 A 1 A
Some spots…
3 A
Most of the time :
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
filter
DIY electron spectrometer – just a few pictures
Positive magnetic field
Negative magnetic field
• There is an effect compatible with an electron signal (up to 500 keV)• We haven’t a real « zero » position• Huge spread of the spot, non-reproducibility• No calibration number of electrons – light intensity 13
Needs a collimator !B
increasing
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
14
• 2 structures tested last year : HDS4_thick showed poor performances C30-speed bump gave better results But remember the cumulative duration of the tests is still short compared to
SLAC tests (less than 33 h in total for 2008).
Conclusion and future plans
• C30-sb manufactured following the same procedure as the T18 X-band structure currently tested at SLAC with bad results.
• Spectrometer measurement performed with what was at hand, definitely lacks a collimator !
• Poor reproducibility, we are working to see if it can be related to the position of the breakdown (structure acting as a collimator).
• Nevertheless gave indications of an e- “beam” emmitted during the breakdown with an energy up to at least 500 keV.
• ONE last 30 GHz structure to be tested in 2009 (TM02), optical spectrometry measurement will be done (J. Kovermann).
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
15
Many thanks :
Alexandra AnderssonJan KovermannSteffen Döbert
Riccardo Zennaro
and for your attention !
to
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
16
65 70 75 80 85 90 95 100
10-6
10-5
10-4
10-3
10-2
Peak gradient (MV/m)
Bre
akdo
wn
rate
C30-sb
In blue : my analysisIn green : Steffen’s one
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
17
75 80 85 90 95 100
10-5
10-4
10-3
10-2
Peak gradient (MV/m)
Bre
akdo
wn
rate
C30-sb-reversed
1
2
3
4
5
67
Slight improvement with time
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
18
70 75 80 85 90 95 10010
-6
10-5
10-4
10-3
10-2
Peak gradient (MV/m)
Bre
akdo
wn
rate
3.5 mm reversed speed bump turned Steffen3.5 mm reversed speed bump Mathias
Slope difference : 0.2 %
Different points ↔ different analysis(file by file for Steffen’s analysis, single file combining the whole history for mine).
C30-sb-reversed
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
19
45 50 55 60 65 70
10-4
10-3
Peak gradient (MV/m)
Bre
akdo
wn
rate
HDS4_thick re-test : ``results´´
Upper limit
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
20
0 5 10 150
20
40
60
80
100
120
Time (h)
Acc
eler
atin
g gr
adie
nt
0 5 10 150
20
40
60
80
100
120
Time (h)
Puls
e le
ngth
@ 50%@ 75%
HDS4_thick beginning of the test
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
21
Energie(keV)
Vitesse(m/s)
R( 0.15 mT)(m)
R(0.75 mT)(m)
R(1.5 mT)(m)
R(4.5 mT)(m)
R(7.5 mT)(m)
R(9 mT)(m)
R(15 mT)(m)
X( 0.15 mT)(m)
X(0.75 mT)(m)
X(1.5 mT)(m)
X(4.5 mT)(m)
X(7.5 mT)(m)
X(9 mT)(m)
X(15 mT)(m)
0.1 A 0.5 A 1.0 A 3.0 A 5.0 A 6.0 A 10.0 A 0.1 A 0.5 A 1.0 A 3.0 A 5.0 A 6.0 A 10.0 A
10000 2.99E+08 1.86E+02 3.72E+01 1.86E+01 6.20E+00 3.72E+00 3.10E+00 1.86E+007.52E-05 3.76E-04 7.50E-04 2.23E-03 3.70E-03 4.43E-03 7.28E-03
5000 2.99E+08 1.13E+02 2.27E+01 1.13E+01 3.78E+00 2.27E+00 1.89E+00 1.13E+001.23E-04 6.16E-04 1.23E-03 3.64E-03 6.01E-03 7.17E-03 1.17E-02
3000 2.97E+08 7.49E+01 1.50E+01 7.49E+00 2.50E+00 1.50E+00 1.25E+00 7.49E-011.87E-04 9.30E-04 1.85E-03 5.47E-03 8.97E-03 1.07E-02 1.74E-02
2000 2.94E+08 5.38E+01 1.08E+01 5.38E+00 1.79E+00 1.08E+00 8.96E-01 5.38E-012.60E-04 1.29E-03 2.57E-03 7.55E-03 1.23E-02 1.47E-02 2.38E-02
1000 2.82E+08 3.14E+01 6.29E+00 3.14E+00 1.05E+00 6.29E-01 5.24E-01 3.14E-014.44E-04 2.20E-03 4.36E-03 1.26E-02 2.05E-02 2.44E-02 3.98E-02
500 2.59E+08 1.94E+01 3.87E+00 1.94E+00 6.46E-01 3.87E-01 3.23E-01 1.94E-017.20E-04 3.55E-03 7.00E-03 2.00E-02 3.24E-02 3.88E-02 6.96E-02
200 2.08E+08 1.10E+01 2.20E+00 1.10E+00 3.66E-01 2.20E-01 1.83E-01 1.10E-011.27E-03 6.19E-03 1.21E-02 3.43E-02 5.88E-02 7.60E-02 #NUM!
100.00 1.60E+08 7.17E+00 1.43E+00 7.17E-01 2.39E-01 1.43E-01 1.20E-01 7.17E-021.93E-03 9.36E-03 1.81E-02 5.32E-02 1.51E-01 #NUM! #NUM!
10.00 5.80E+07 2.24E+00 4.48E-01 2.24E-01 7.47E-02 4.48E-02 3.74E-02 2.24E-026.07E-03 2.82E-02 5.73E-02 #NUM! #NUM! #NUM! #NUM!
1.00 1.80E+07 6.84E-01 1.37E-01 6.84E-02 2.28E-02 1.37E-02 1.14E-02 6.84E-031.90E-02 2.30E-01 #NUM! #NUM! #NUM! #NUM! #NUM!
0.10 5.90E+06 2.24E-01 4.48E-02 2.24E-02 7.46E-03 4.48E-03 3.73E-03 2.24E-035.75E-02 #NUM! #NUM! #NUM! #NUM! #NUM! #NUM!
Spectrometer calculations
RLRL
lLdXarcsintan1
arcsintan)(
α
α
B
R
L
lXd
45°
Speed bumpstructure
magnet
Alumina screen
22
DIY electron spectrometer – ``statistical´´ analysis
Increasing B field
See Jan’s presentation on February, 18th
Mathias Gerbaux - CTF3 Collaboration Technical meeting - 27/01/2009
23
Same phase advanceSame P/cSame aperture and iris shapeSame field configuration in the iris region
but
Different group velocity: 4.7% & 2%Different R/Q: 29 kΩ/m & 12 kΩ/m
TM02 structure
Is it possible to change some global parameter without changing local field distribution?
Only by changing the propagating mode
TM02 regular cell
TM01 regular cell “reference”
Test structure in disks: 30 cell and identical mode launcher of the “conventional” 2π/3 Ø 3.5 mm
Courtesy of
Riccardo
24as ds vgs( ) a1 d1 vg1( )
TM01: 2π/3 Vg=4.7%
TM02: 2π/3 Vg=2.0%a
Vg
d
Direct comparison of Vg
Courtesy of
Riccardo
25
Why speed bump?
From Igor’s presentation at the X band workshop:
Very often we do observe, that after accelerating structure processing the most of the surface modifications take place in a few first cells. Also the number of cells involved is correlated with the group velocity, the less the Vg the fewer cells modified.
What do we certainly know, the breakdown ignition is a very fast process: 0.1 -10 ns. If so, one can propose the main difference between the “first” and “second” cell is accessible bandwidth.And the lower group velocity the more the difference.The first cell, if breakdown occurs is loaded by the input coupler/waveguide and is very specific in terms of bandwidth. Other words, the first cell can accept “more” energy during breakdown initiation then consequent ones. Worse to mention that we do not know the exact transient behavior of the breakdown and the structure bandwidth could play important role.
We can tray by reducing vg in the matching cell
HDS 60 L
PINC
HDS 60 S
PINC
Courtesy of
Riccardo
Je ne sais pas si la vidéo restera longtemps à cette adresse mais pour le moment, vous pouvez écouter l’intégralité du « discours à l’occasion du lancement de la réflexion pour une Stratégie Nationale de Recherche et d’Innovation » de Sarkozy. Attention cependant, ses putains d’accents poujadistes et sa façon de nous prendre pour des cons sont susceptibles de vous mettre de très très mauvaise humeur !http://www.elysee.fr/accueil/Bonne journée quand même…