1. Performance of Large Grain TESLA cavities
D. Kostin and J. Sekutowicz
LCWS2017

2. Introduction Vertical tests Performance in CM Final remarks Outline
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

3. TESLA/ILC superconducting cavity*
Introduction
TESLA/ILC superconducting cavity*
L-Band 1.3 GHz 9-cell standing wave accelerating structure.
The structure is asymmetric. The end-cells have different shape for better damping of non-propagating dipole HOMs.
It is equipped with 2 HOM couplers, pickup and FPC ports.
It is made of high purity Nb, usually fine grain (<100µm) but several were built of large grain Nb.
(*) J.S. “MULTI-CELL SUPERCONDUCTING STRUCTURES FOR HIGH ENERGY e+e- COLLIDERS AND FREE ELECTRON LASER LINACS”, Monograph in Series on Accelerator Physics, Publishing House of Warsaw University of Technology, ISBN , 2008, also published by CERN.
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

4. Possible Large Grain cavities advantages for ILC:
Introduction
Possible Large Grain cavities advantages for ILC:
Lower material and production costs - no rolling, thinner damaged layer, no sheets scanning needed.
High intrinsic Q0, lower operation costs, less expensive cryoplant.
High gradients are possible – Vertical Test Eacc.max → 46 MV/m was demonstrated.
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

5. Large Grain cavities at DESY
Introduction
Large Grain cavities at DESY
RI company has built 11 LG TESLA cavities for DESY.
Ingot diameter was too small to fabricate 1.3GHz elliptical cells.
The sheets have been rolled to increase the diameter.
The grain (crystal) size is ca. ~7 cm.
7 LG cavities has been assembled in a E-XFEL like cryomodule.
Large Grain cavities at Institute of Heavy Ione Physics (PKU)
Six TESLA cavities have been built by Ninxia company for IHIP.
Grain size is ca. 3cm.
They have been tested after BCP treatment .
One cavity was shipped to DESY for the EP treatment and test.
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

6. Large Grain cavities at DESY, after EP and 120° bake
Vertical tests
Large Grain cavities at DESY, after EP and 120° bake
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

7. Large Grain cavities at DESY
Vertical tests
Large Grain cavities at DESY
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

8. Large Grain cavities at IHIP (PKU)
Vertical tests
Large Grain cavities at IHIP (PKU)
6 PKU LG cavities after BCP treatment:
Courtesy Jiankui Hao
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

9. Short pulse mode (nominal E-XFEL): 1.3ms pulses @ 10 Hz
Performance in CM
7 cavities LG have been assembled in the XM-3 together with one made of FG niobium.
Short pulse mode (nominal E-XFEL): 1.3ms 10 Hz FG
Performance of cavities: operational <Eacc> = 33.3 MV/m
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

10. 4.1×1010 4.7×1010 2.04×1010 2.1×1010 2.33×1010 3. Performance in CM
XM-3 has been tested also in CW and long pulse (LP) mode, with pulses were up to 520 ms long and repetition rate of 1 Hz.
The highest gradient for LP mode was 20.1 MV/m with DF=43.2%.
Demonstrated Q0 in the SP/ LP/CW operation modes at 1.8K and 2K
Temp
short pulse (SP)
long pulse (LP) CW
1.8 K -
4.1×1010
4.7×1010
@ 9.5MV/m 2K
2.04×1010
24 DF=1%
2.1×1010
2.33×1010
@17.2 MV/m
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,

11. Thank you for your attention
4. Final remarks
SP operation possible up to at least 33 MV/m.
At 24 MV/m Q0 ≳ in SP operation mode.
For LP operation at ca. 15 MV/m, 1.8K.
We will test XM-3 soon again at 1.8K in CW/LP modes at higher gradients.
DESY will do EP on IHIP cavity and test it at 2K and 1.8K.
Thank you for your attention
D. Kostin, J. Sekutowicz, Performance of Large Grain Tesla cavities, LCWS2017,