td18 high power test results faya wang chris adolphsen may 3, 2010
DESCRIPTION
a [mm] a/ (%) d [mm] e f [GHz] Q(Cu) vg/c [%] r’/Q [LinacΩ/m] Es/Ea Hs/Ea [mA/V] Sc/Ea 2 [mA/V] For regular cells P = 59.8 MW for = 100 MV/m Active Length = 15.8 cm FirstMiddle Last Cell TD18 Parameters A. GrudievTRANSCRIPT
TD18 High Power Test ResultsFaya Wang
Chris AdolphsenMay 3, 2010
In NLCTA Beamline Structure Note Performance
4/08 – 7/08T18vg2.6-Disk
SLAC_1Cells by KEK,
Assembled at SLAC
Good: 105 MV/m, 230 ns at LC BDR spec of 8e-7/pulse/m but hot cell
developed
7/08 – 10/08T18vg2.6-Disk
SLAC_1Powered from
Downstream EndGood: 163 MV/m, 80 ns, 2e-5 BDR in last cell, consistent with fwd operation
12/08 – 2/09T18vg2.6-Disk
CERN_1CERN Built, Operate
in Vac CanVery Poor: very gassy with soft breakdowns at 60 MV/m, 70 ns
Test at KEK10/08 – 06/09
T18vg2.6-DiskKEK_1
Cells by KEK, Assembled at SLAC
Good: 102 MV/m, 240 ns at LC BDR spec – no bkd location info
7/09 – 8/09T24vg1.8Disk
CERN_1CERN Built, Cells
Pre-FiredPoor: achieve < 60 MV/m after 100 hours with pulse lengths < 100 ns
5/09 - presentT18vg2.6-Disk
SLAC_2Cells by KEK,
Assembled at SLACGood: after 280 hours, 97 MV/m, 230 ns
at LC DBR spec – one hot cell
12/09 -4/10TD18vg2.3-Disk
SLAC_1Cells by KEK,
Assembled at SLACFair: after 1000 hours, 81 MV/m, 230 ns
at LC DBR spec – no hot cells
CLIC Disk Structure Tests
a [mm] 4.06 3.36 2.66a/l (%) 15.4 12.8 10.1d [mm] 2.794 2.054 1.314e 1.21 1.18 1.15 f [GHz] 11.424 11.423 11.424Q(Cu) 5098 5364 5458vg/c [%] 2.25 1.47 0.87r’/Q [LinacΩ/m] 10195 12560 15034Es/Ea 1.97 1.88 1.88Hs/Ea [mA/V] 5.85 5.2 4.85Sc/Ea2 [mA/V] 0.52 0.39 0.3
0 100 200 300 400 500 600 700 800 900 10000
5
10
15
20
25
n
|Ez|
[kV
/m]
For regular cellsP = 59.8 MW for <G> = 100 MV/m
Active Length = 15.8 cm
First Middle Last Cell
TD18 Parameters
A. Grudiev
TD18 Parameter Plots for an Unloaded Gradient of 100 MV/m
0 2 4 6 8 10 12 14 16 180
50
100
150
200
250
iris number
P [M
W] (
blac
k), E
s (gre
en),
Ea (r
ed) [
MV/
m],
T
[K] (
blue
), S
c*50
[MW
/mm
2 ] (m
agen
ta)
29.1
47.0
155
226
3.2
4.4
79
120
57.5
34.3
Pinload = 57.5 MW, Pout
load = 34.3 MW Eff = 0.0 % tr = 0.0 ns, tf = 0.0 ns, tp = 100.0 ns
High T : 47 degCfor 100 ns Pulsewhereas T18 is only 12.5 degC
0 5 10 15 200
50
100
150
200
250
iris number
T18 vg2p6 disk
8.1 12.5
148
232
2.7
4.4
76
126
53.037.4
T18
Last Cell Surface Magnetic Field
High Power Operation History
Final Run at 230 ns: 94 hrs at 100 MV/m w BDR = 7.6e-5 60 hrs at 85 MV/m w BDR = 2.4e-6
0 200 400 600 800 1000 12000
20
40
60
80
100
120
140
Accumulated rf process time (hr)
BDR (1/hr)<G> for regular cell (MV/m)Pulse width (divided by 10) (ns)
BDR Evolution with RF Processing
0 500 1000 150010
-6
10-5
10-4
10-3
RF Process Time (hr)
BD
R (1
/pul
se/m
)
100MV/m@100ns100MV/m@150ns100MV/m@200ns100MV/m@230ns
0 1000 2000 3000 400010
-6
10-5
10-4
10-3
Accumulated Breakdown Events
BD
R (1
/pul
se/m
)
100MV/m@100ns100MV/m@150ns100MV/m@200ns100MV/m@230ns
TD18 Breakdown Location Profile at Different Stages of Processing
0 5 10 15 200
50
100
150
200
250
Regular Cell No.
BD
R E
vent
s
0 ~ 200 hrs200 ~ 400 hrs400 ~ 600 hrs600 ~ 700 hrs700 ~ 960 hrs 0 ~960 hrs
0 5 10 15 200
10
20
30
40
50
Cell No.
Per
cent
of B
KD
Eve
nts
394 BKDs within 0~250hrs193 BKDs within 250~500hrs298 BKDs within 500~750hrs57 BKDs within 750~900hrs74 BKDs within 900~1000hrs34 BKDs within 1000~1200hrs24 BKDs within 1200~1400hrs
Did not find visual evidence related to the hot cell in a post-run boroscope exam – typical of NLC/GLC structures, many of which had hot cells
T18 Breakdown Location Profile at Different Stages of Processing
98 100 102 104 106 108 110 11210
-7
10-6
10-5
10-4
10-3
Gradient (MV/m)
BD
R (1
/pul
se/m
)
500 hr
250 hr
1400 hr
900 hr
1200 hr
TD18 700 hr
Comparison with T18_SLAC1
Pulse width 230ns: Green line for TD18, Others for T18
LC Breakdown Limits• For NLC, the breakdown rate limit was chosen so that the 2% pool of spare rf units
would rarely (once a year) be depleted assuming a 10 second recovery period after each breakdown. Operation with a 10 second recovery period has been demonstrated but longer times (30-100 sec) are typically used since the structure monitoring system has a 30 second sampling period. For 60 Hz operation at NLCTA, the breakdown rate limit translates to 0.1 per hour with the nominal 60 cm long structure design. This choice is somewhat soft in that a four-times higher rate would still provide 99% full-energy availability assuming a 5 second recovery time, which has also been demonstrated.
• For reference, at the 0.1 per hour limit, a breakdown would occur in one of the ~ 20,000 NLC X-Band structures once every 120 pulses. Such breakdowns will degrade the luminosity from that pulse, but the beam kicks from the breakdown fields should not inhibit beam operation.
• To 'translate' this limit, for one bkd in 10 hours in a 0.6 m structure at 60 Hz, the rate is 4.6e-7/pulse/structure or 7.7e-7/pulse/m. For CLIC 3-TeV, this same limit gives 1 bkd per 40 pulses, but because of the smaller beam emittance (and hence a smaller collimator aperture), the kicks are more likely to hit the collimators. The bkd kick distribution measured at NLCTA has values as large as 30 keV/c - this level is < 1/10 of the amount needed to hit the collimators at NLC.
Can TD18 Run with no Recovery Period ?
1 2 3 4 5 6 70
0.1
0.2
0.3
0.4
0.5
0.6
0.7
Frac
tion
of b
reak
dow
n ev
ents
Cascaded events
All eventsMulti-event taken as one event
Type 1 2 3 4 5 6 7
Events 77 23 5 5 1 2 1
33 Hour Test Period
180 185 190 195 200 205 210 215
2468
pulses
Inpu
t ref
(arb
.u.)
24 26 28 30 32 34 362468
1012
pulses
Inpu
t ref
(arb
.u.)
150 160 170 180 190 200 2100
5
10
15
pulses
Inpu
t ref
(arb
.u.)
155 160 165 170 1752468
1012
pulses
Inpu
t ref
(arb
.u.)
Cascaded BDR Test at 100 MV/m @ 200ns
BDR Pulse Width Dependence
50 100 150 200 25010
-6
10-5
10-4
10-3
Pulse Width (ns)
BD
R (1
/pul
se/m
)
@80~140 hr@280~360 hr@700~960 hr
100 150 200 25010
-6
10-5
10-4
Pulse Width (ns)
BD
R (1
/pul
se/m
)
T18, 108 MV/m @ 250 hrsT18, 108 MV/m @ 500 hrsT18, 110 MV/m @900 hrsTD18, 100 MV/m @ 80~140 hrsTD18, 100 MV/m @ 230~360 hrsTD18, 100 MV/m @700~960 hrs
100 MV/m
BDR Pulse Heating Dependence
20 30 40 50 60 70 80 90 10010
-7
10-6
10-5
10-4
10-3
Peak Pulse Heating at Last Cell (K)
BD
R (1
/pul
se/m
)
T18, 900 hrsTD18, 100 MV/m @ 100ns,870hrsTD18, 100MV/m@ 150ns, 960hrs TD18, 100MV/m@200ns, 750hrsTD18, 115MV/m@150ns, 550hrsTD18, 120MV/m@150ns, 570hrsTD18, 100MV/m@230ns, 700hrsTD18, 105MV/m@230ns, 680hrsTD18, 100MV/m@50ns
110 MV/m
1st cell 62% of last cell at pulse heating
Pulse Heating under Different Conditions
0 500 1000 1500 20000
10
20
30
40
50
60
70
80
90
Time (ns)
Pea
k P
ulse
Hea
ting
in L
ast C
ell (
K)
100 MV/m, 100 ns - square pulse
120 MV/m, 100 ns
100 MV/m, 200 ns
115 MV/m,150 ns
100 MV/m, 150 ns
0 500 1000 1500 20000
10
20
30
40
50
60
Pulse Width (ns)
Pow
er to
Strc
utur
e (M
W)
200 ns @ 100 MV/m150 ns @ 100 MV/m
Pulse Heating BDR Test
0 500 1000 1500 2000-10
0
10
20
30
40
50
60
70
Time (ns)
Pow
er to
Stru
ctur
e (M
W)
150ns - normal150ns - pre heating
0 500 1000 1500 20000
20
40
60
80
Time (ns)
Pea
k P
ulse
Hea
ting
in L
ast C
ell (
K)
100 MV/m, 200 ns100 MV/m, 150 ns100 MV/m, 150 ns pre-heating
60 65 70 750.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
Peak Pulse Heating in Last Cell (K)
BD
R (1
/hou
r)
100MV/m@150ns100MV/m@150ns + pre-heating100MV/m@200ns
TD18 Summary• Structure performed worse than T18 even though it did not have
any hot cells. TD18 bead pull data also shows a large phase advance change unlike that for T18 where no change is observed (see Juwen’s talk).
• BDR pulse heating dependence suggests that operation above 50 degC may be a factor (as it appears to be in single SW cell data)
• Pre-heating test at constant gradient confirms the pulse heating sensitivity (although the statistics are low) – Factor of ~ 3 BDR increase similar to that seen with no pre-
heating for the same temperature range. • Perhaps should not draw too strong of conclusion given that this is
just one structure, and the KEK TD18 results are even more puzzling.