1. Radiation Safety Considerations of C100 Cryomodule Operation
P. Degtiarenko, J. Jefferson, M. Keller, G. Kharashvili, V. Vylet, K. Welch, M. Washington
Radiation Control Department Jefferson Lab
Title Page

2. electron field emission
C100 – field emitted electrons may accelerate to energies well above photonuclear reaction thresholds
Prompt photon and neutron fields – problem at cryomodule test facilities;
Material activation – planning accelerator maintenance, possible relocation of parts, decommissioning;
Radiation damage to nearby electronics and materials.
Sourceterm difficult to characterize;
May vary with time;
Challenging to simultaneously model all physical processes involved.
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

3. electron field emission
Low energy electrons below photonuclear reaction thresholds
Electrons capable of accelerating up to the full gradient
Iris
Electromagnetic cascade ҉
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High energy cascade develops at the end flange at the cryomodule step-down.
CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

4. C100s at Jefferson Lab Radiation surveys; Prompt radiation monitoring;
Correlating accelerating gradients and prompt radiation fields;
Gamma spectroscopy analysis of activated components
Portable HPGe detector
GENIE-2000
ISOCSTM
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5. Prompt radiation - SL24 & SL25
108
107
106
105
104
103
102 10 1
10-1
10-2
(μSv / h )
(mGy / h )
10-3
10-4
10-5
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

6. Gamma spectroscopy analysis
Nuclide
T1/2 (day)
Na-24
0.62
Ni-57
1.48
Sc-47
3.35
Mn-52
5.59
Ni-56
6.08
NB-92m
10.2
V-48 16
CR-51
27.7
Fe-59
44.5
CO-58
70.9
CO-56
77.3
Sc-46
83.8
ZN-65
244.3
CO-57
271.8
MN-54
312.3
NA-22
803.6
CO-60
1924.9
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Pulse height spectrum– 2m from beamline between NL25-NL26
CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

7. NL25 accelerating gradients
Data missing
NL25 Total Gradient
2.3 GeV
push
radcon test
NL25 Individual Cavity Gradients
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

8. SL24 accelerating gradients
Data missing
SL24 Total Gradient
2.3 GeV
push
radcon test
SL24 Individual Cavity Gradients
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab
CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

9. Activation rates
Assuming that all radioactivity was produced during the first 5 days of February 2014 – push for 2.3 GeV – radionuclide production rates were calculated.
Expected levels of radioactivity and subsequent dose equivalent rates are then projected for 3-month, 1-year, and 5-year long runs.
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10. NL25 forecast Interior Page Design 1
CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

11. SL24 forecast Interior Page Design 1
CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

12. Conclusions
High radiation areas are expected near C100s for hours after each typical high gradient run, but not above 1R/h requiring physical barriers.
Radiation areas are likely to persist for longer periods of time – for weeks or months.
Radiological controls in CEBAF tunnel will have to change accordingly.
Prompt neutron field measurements can be used to minimize activation.
Further studies:
Continue surveying the areas;
Gamma spectroscopy during accelerator downs;
Investigate neutron monitoring options.
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

13. Conclusions
Besides activation, neutron measurements may be useful for a number of operational issues
Heat
Vacuum
Radiation damage
Neutron monitoring can be used as an additional tool in optimizing cryomodule performance.
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CEBAF SRF/RF/CRYO Workshop, 3 April 2014, Jefferson Lab

14. acknowledgements
Thanks to the members of the Field Operations Group of Radiation Control Department, Accelerator Operations Department, and Institute for SRF Science and Technology for their contributions.
This work was supported by the U.S. Department of Energy under contract number DE-AC05-06OR23177s
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15. references
P. Degtiarenko, M. Keller, G. Kharashvili, V. Vylet, K. Welch , “Radiation Safety Consideration of C100 Cryomodule Operation at Jefferson Lab”, JLAB-TN , Newport News, 2012.
M. Silari, S. Agosteo, J.-C. Gaborit and L. Ulrici, "Radiation produces by the LEP superconducting RF cavities," Nuclear Instruments and Methods in Physics Research A, vol. 432, pp. 1-13, 1999.
R. J. Hernandez Pinto, M. Otto and M. Valentan, "Radiation Measurements in the FLASH Tunnel," DESY Technical Note , Hamburg, Germany, 2006.
K. Welch, V. Vylet and B. May, "Lessons Learned: SRF Testing and Activated Components," Accelerator Safety Workshop, Argon National Lab, 2011.
F. Marhauser, "Field Emission and Consequences as Observed and Simulated for CEBAF Upgrade Cryomodules," MuPlus Inc. and Jefferson Lab, JLAB-TN , Newport News, 2012.
C. Ginsburg and I. Rakhno, "Shielding studies for superconducting RF cavities at Fermilab," in Shielding Aspects of Accelerators, Targets and Irradiation Facilities (SATIF), Geneva, Switzerland, 2010.
C. Ginsburg and I. Rakhno, "Optimization Studies for Radiation Shielding of a Seperconducting RF Cavity test Facility," in International Particle Accelerator Conference (IPAC), Kyoto, Japan, 2010.
E. Donoghue, G. Wu, J. Mammosser, R. Rimmer, M. Stribet, L. Phillips and H. Wang, "STUDIES OF ELECTRON ACTIVITIES IN SNS-TYPE SUPERCONDUCTING RF CAVITIES," in The 12th International Workshop on RF Superconductivity, Ithaca, New York, 2005.
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