A method of producing very high resistivity surface conduction on ceramic accelerator components using metal ion implantation Page: 3 of 3
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by using RBS, is not feasible because of the surface
roughness of the alumina, but we can make a good
estimate of the profile using the TRIM code , which
carries out a Monte Carlo calculation of the transport of
ions in matter. For Pt into alumina at 77 keV, the range
(distance below the surface to the peak of the distribution)
is 220 A and the straggling (HWHM of the distribution)
Dose (ions10 s cm2)
Figure 3 Resistivity vs. Dose
Three "production" cylinders were implanted. Each
acquired nearly the desired resistance at 18 GQ +- 5% (54
Gfl/square). A negative temperature effect was observed
with a rise in resistivity of 50% upon cooling from the
60 C implantation temperature to room temperature. The
resistance at 20 C should dissipate 3.5 W per cylinder at
design voltage, well below a power that could cause a
thermal run-away. Two cylinders have been assembled
into an insulating column assembly, installed in the gun,
baked out at 250 C for several days and subsequently
conditioned up to 420 kV. In situ resistance measurement
of one cylinder, with vacuum on the inside and room air
on the exterior, yielded a value of approximately 13 GO.
The nearly 1/3 drop is considered an effect of the
conditions of measurement and attachment. No voltage
dependence was seen in the in situ measurements using
voltages of 10 to 100 kV.
Using a conservative approach, the gun has
subsequently been run at 350 kV for collection of a data
set at this value. (Before upgrade to the new ceramic
insulating cylinders, the data sets were taken at 250 kV
and 300 kV.) Conditioning the gun at 500 kV+ and
operation at 500 kV awaits production of a spare ceramic
cylinder set and success at intermediate voltages.
4 DISCUSSION AND CONCLUSION
Unlike the original methods tried, Metal Ion Implantation
achieved the goal of obtaining the tens of GS2 value
resistance required. The accuracy achieved was of a
different class than the original methods, far more accurate
because of the ability to monitor the decreasing resistance
during the process. The method is also well suited to be
the final process in a production sequence, where risky
value-added features are already applied to ceramics before
this high-value-added step. Note that before the
continuous resistance monitoring feature was installed on
the rotisserie, an implantation attempt undershot the
target resistance. The cylinder was recovered to original
condition by a simple sanding with diamond grit. The ion
implantation method also appears to be well suited to the
gun application, withstanding the bakeout and exhibiting
no voltage dependence. However, more running experience
would allow a firmer statement. The steep negative
temperature dependence could result in thermal runaway
for applications that have too low initial resistance and
inadequate cooling. The investment in hardware and
experience is now substantial and the ion implantation
group at LBNL is ready to use this method in other
 R. V. Latham, "High Voltage Vacuum Insulation: The
Physical Basis", Academic Press, Inc. (London) Ltd.
 C. K. Sinclair, "A 500 kV Photoemission Electron Gun
for the CEBAF FEL", Nucl. Instrum. Methods
A318(1992) p.# 410.
 US Patent #3,729,575 granted to Maynard C. Harding &
Joseph A. Payne, Litton Systems Inc., filed October 28,
1971, granted April 24, 1973.
 S. Anders, A. Anders, L G. Brown, "Surface Resistivity
Tailoring of Ceramic Accelerator Components", Proc.
1993 Particle Accelerator Conf., Washington D.C.,
IEEE (1993) p.# 1390
 1 G. Brown, M R Dickinson, J. E. Galvin, X. Godechot
and R. A. MacGill, "Versatile high current metal ion
implantation facility", Surf. Coat. Technol. 84 (1992)
 I. G. Brown, "Vacuum arc ion sources for particle
accelerators and ion implantation", IEEE Trans. Plasma
Sci. 21, 537 (1993).
 .G. Brown, A. Anders, S. Anders, M. R. Dickinson, R.
A. MacGill and E. M. Oks, "Recent advances in vacuum
arc ion sources", Surface and Coatings Technol. 4, 550-
 F. Liu, O. R. Monteiro, K. M. Yu and I.G. Brown, "Self-
Neutralized Ion Implantation into Insulators", submitted
to Nuci. Insetrum. Meth. B.
 LG. Brown and X. Godechot, "Vacuum arc ion charge
state distributions", IEEE Trans. Plasma Sci. PS-19, 713
 See, for instance, L.C. Feldman and J. W. Mayer,
Fundamentals of Surface and Thin Film Analysis, (North
Holland. NY, 1986).
 J. P. Biersack, S. Berg and C. Nender, Nucl. Instrum.
Meth. Phys. Res. B59/60, 21 (1991).
Work was supported by the U.S. DOE under Contract
Number DE-ACO5-84ER40150 and the LBNL group was
- supported by the U.S. DOE, under Contract Number DE-
AC03-76SF00098. F. Liu was supported as a visiting
scientist at LBNL from Beijing Normal University by the
3 University of California Education Abroad program.
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Liu, F.; Brown, I.; Phillips, L.; Biallas, G. & Siggins, T. A method of producing very high resistivity surface conduction on ceramic accelerator components using metal ion implantation, article, May 1, 1997; Newport News, Virginia. (digital.library.unt.edu/ark:/67531/metadc704135/m1/3/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.