NASA Technical Reports Server (NTRS) 20170001264: 12CaO-7Al2O3 Electride Hollow Cathode

1.1 MB·English

by  NASA Technical Reports Server (NTRS)

1111111111111111111inmuuu~
(12) United States Patent (io) Patent No.: US 9,552,952 B2
Rand et al. (45) Date of Patent: *Jan. 24, 2017
(54) 12CAO-7AL2O3 ELECTRIDE HOLLOW (52) U.S. Cl.
CATHODE CPC .................. HOIJ 1/025 (2013.01); HOIJ 1/14
(2013.01); HOIJ 27/08 (2013.01); HOIJ
(71) Applicant: COLORADO STATE UNIVERSITY 27/146 (2013.01)
RESEARCH FOUNDATION, Fort (58) Field of Classification Search
Collins, CO (US) CPC ....................... HOIJ 27/00 27/26; HOIJ 1/025
See application file for complete search history.
(72) Inventors: Lauren P. Rand, Wayland, MA (US);
John D. Williams, Fort Collins, CO (56) References Cited
(US); Rafael A. Martinez, Fort Collins,
U.S. PATENT DOCUMENTS
CO (US)
2,894,054 A 7/1959 Cameron et al.
(73) Assignee: Colorado State University Research 5,970,993 A 10/1999 Witherspoon et al.
Foundation, Fort Collins, CO (US) 6,427,757 B1 8/2002 Tilak
9,305,733 132 * 4/2016 Rand ....................... HO1J 1/025
(*) Notice: Subject to any disclaimer, the term of this 2005/0061657 Al 3/2005 Hosono et al.
patent is extended or adjusted under 35 (Continued)
U.S.C. 154(b) by 0 days.
OTHER PUBLICATIONS
This patent is subject to a terminal dis-
claimer. International Searching Authority, International Search Report, Sep.
26, 2014, PCT/US14/35747, pp. 1-11.
(21) Appl. No.: 15/091,433
(Continued)
(22) Filed: Apr. 5, 2016
Primary Examiner Mariceli Santiago
(74) Attorney, Agent, or Firm Cochran Freund &
(65) Prior Publication Data
Young LLC; Samuel M. Freund
US 2016/0217961 Al Jul. 28, 2016
(57) ABSTRACT
Related U.S. Application Data
The use of the electride form of 12CaO-7A'2031 or C12A7,
(63) Continuation of application No. 14/263,970, filed on as a low work function electron emitter in a hollow cathode
Apr. 28, 2014, now Pat. No. 9,305,733. discharge apparatus is described. No heater is required to
initiate operation of the present cathode, as is necessary for
(60) Provisional application No. 61/816,593, filed on Apr. traditional hollow cathode devices. Because C12A7 has a
26, 2013. fully oxidized lattice structure, exposure to oxygen does not
degrade the electride. The electride was surrounded by a
(51) Int. Cl. graphite liner since it was found that the C12A7 electride
HOIJ 27/14 (2006.01) converts to it's eutectic (CA+C3A) form when heated
HOIJ 27/08 (2006.01) (through natural hollow cathode operation) in a metal tube.
HOIJ 1/02 (2006.01)
HOIJ 1/14 (2006.01) 29 Claims, 11 Drawing Sheets
M
US 9,552,952 B2
Page 2
(56) References Cited
U.S. PATENT DOCUMENTS
20 09/022 421 4 Al 9/2009 Hosono et al.
2012/0001539 Al 1/2012 Rueger et al.
2013/0088141 Al 4/2013 Miyakawa et al.
OTHER PUBLICATIONS
Rand et al., "C12A7 Electride Hollow Cathode", Conference Paper,
DTIC Online Information for the Defence Community, pp. 1-8,
Mar. 2013.
Domonkos et al., "Parametric Investigation of Orifice Aspect-Ratio
on Low Current Hollow Cathode Power Consumption", American
Institute of Aeronautics, pp. 1-10, 1998.
Goebel et al., "Chapter 6: Hollow Cathodes", Apr. 17, 2008, pp.
243-323.
* cited by examiner
U.S. Patent Jan. 24, 2017 Sheet 1 of 11 US 9,552,952 B2
FIG. l
U.S. Patent Jan. 24, 2017 Sheet 2 of 11 US 9,552,952 B2
16
is
12
l5b
3o
22
U.S. Patent Jan. 24, 2017 Sheet 3 of 11 US 9,552,952 B2
co
N
u-
N
Nr
U.S. Patent Jan. 24, 2017 Sheet 4 of 11 US 9,552,952 B2
CD
E
Q)
E
U.
0In
0
0 0 0 0 0 d 0 0 ~D 0 0
0
0
5
3

0
0
0

0
5
2

0
0
2
)
n
i
m
( .
e G
m I
i
T F
0
5
1

0
0
1

0
5

0
t7 00 0 50 00 50 00
W 2 1 0 0 9 0
1 1 1 1
a g
lf-S- dellauJ tuu' Zb` ZOiL sNaJ 9 O3 ti 11S 6`SSZ`6SZ SZ
w
1.1
m
A
j,".
)IC
nc
)N
)V( egatloV edonA
lf-S- dellauJ tuu' Zb` ZOiL SuaaJ L O3 tI 11S 6`SSZ`6SZ SZ
mI
Qr
3N
0
M DC
a
)G
aeeeew
m
.3~
.AR
m
x o 0 o e a x x x
0 0 0 0 a a
)V( egatloV edonA
U.S. Patent Jan. 24, 2017 Sheet 8 of 11 US 9,552,952 B2
FIG. 7