7835 Lifetime Analysis
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7835 Lifetime 7835 Lifetime Analysis Analysis Elliott McCrory December 15, 2004
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7835 Lifetime Analysis. Elliott McCrory December 15, 2004. 7835 Basic Information. 5 MW, 201.25 MHz Power Amplifier Original model 4617 Difference: Thoriated filament Matched driver, model 4616 We use at 175 kW, 201 MHz Capability: Up to 2 MW for very short pulses 195 to 600 MHz - PowerPoint PPT Presentation
Transcript of 7835 Lifetime Analysis
7835 Lifetime 7835 Lifetime AnalysisAnalysis
Elliott McCroryDecember 15, 2004
7835 Basic Information7835 Basic Information 5 MW, 201.25 MHz Power Amplifier
Original model 4617• Difference: Thoriated filament
Matched driver, model 4616• We use at 175 kW, 201 MHz• Capability:
– Up to 2 MW for very short pulses– 195 to 600 MHz
Burle Industries, Lancaster, PASpun off from RCA in 1987
Remember: An average year is 8766 hours
The The 7835: 7835: Sliced!Sliced!
Getter
Anode
Cathode/Filament
Ion Pumpwould go
here
Pinch-off
Current users of 7835Current users of 7835 Fermilab
5 sockets; 8000 hours/year Brookhaven Lab
9 sockets; ~4000 hours/year Argonne
1 socket; <1000 hours/year Los Alamos
5 sockets; ?? Quadulan Islands (DOD)
4 sockets; 8000 hours/year??4617 model tube
Costs/FailuresCosts/Failures Costs
New: $150,000Rebuild: $50k to $120k
• Num rebuilds: Have seen R9Rebuild as good as new~1/5 attempts to rebuild fail
• More or less independent of rebuild number Failures
Half fail due to emission limitHalf fail for other reasons
• Water leaks• Irreparable sparks
– We can repair some sparks locally• Vacuum failure
0
5000
10000
15000
20000
25000
30000
Novem
ber-68
Novem
ber-72
Novem
ber-76
Novem
ber-80
Novem
ber-84
Novem
ber-88
Novem
ber-92
Novem
ber-96
Novem
ber-00
Novem
ber-04
Running Average: 10
Date Received vs. Hours to Date Received vs. Hours to EOLEOL
In Service
Reached End Of Life
BurleRCA
Date Tube Received by Fermilab
11
/19
68
11
/20
04
11
/19
72
11
/20
00
Tube Lifetime HistogramTube Lifetime Histogram
0
5
10
15
20
25
Hours accumulated on a tube
dN/dHR
Last 5 years
0
2
4
6
8
10
12
14
1619
69
1970
1971
1972
1973
1974
1975
1976
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
Number Tubes Received Per Number Tubes Received Per yearyear
Average: ~6/year
0
5000
10000
15000
20000
25000
30000
Au
gu
st-94
Au
gu
st-95
Au
gu
st-96
Au
gu
st-97
Au
gu
st-98
Au
gu
st-99
Au
gu
st-00
Au
gu
st-01
Au
gu
st-02
Au
gu
st-03
Au
gu
st-04
Median since 1/1/2001: 5469 hours
Date Received vs. Hours to Date Received vs. Hours to EOLEOLMedian life: 11791 hrs; RMS = 8000 hrs, Standard Error = 8000/sqrt(n) = 1153 hrs
Brookhaven’s Data (Thru Brookhaven’s Data (Thru 4/03)4/03)
R0 R1 R2 R3 R4 R5 R6 R7Best Tube 18075 38504 27210 24639 27186 33331 27607 11984.31
Worst Tube 3230 3584 100 167.8 20 0 7355.8 9825
Average Life 14194.3 13834.48 9856.5 11447.75 9720.81 11148.9 16745.9 10904.67
Average Tube Lifetime at Brookhaven12203 hours
What Has Happened??What Has Happened?? RCA became Burle in 1987
Some expertise retired This tube is half engineering and
half artwork (it seems) Many (most?) of the original
experts/artisans have now retiredSome (most?) apprentices were
properly trained, but some not!Example: Anode temperatureExample: Getter decision
How Many Burned Up Per How Many Burned Up Per Year?Year?
AssumingMedian life of 11800 hours (~25000 T1)
1.48 (3.0 @T1) years of tube life1 year = 8000 hours
• Or ~4.5 weeks off per year Then we need
N = ΣS [ 1 / LSi ]• S is the number of sockets• L is the median lifetime of the tube in a socket
(4 tubes/1.48 yrs) + (1 tube/3 yrs, T1) 3.04 tubes/year
Assuming EOL at 5500 hours (0.69 years):6.13 tubes/year
1.0
10.0
100.0
0 2000 4000 6000 8000 10000 12000 14000 16000 18000 20000
Median Tube Lifetime
Nu
mb
er
of
Tu
be
s n
ee
de
d p
er
ye
ar
Number Tubes Needed vs. Number Tubes Needed vs. LifetimeLifetime
We Are Here
Burle Average Flux
But Might Be Here
Stable Operation Today?Stable Operation Today? 2001:
March• 5 spares and 2 deliveries imminent—Wow!• Division Management pleads to reduce expenses• Decision by Webber and me (~march 01) not to
order rebuilds– Oops!
June 22 through October 1, 2001• Replaced 6 tubes, leaving 1 spare
Were forced to borrow tubes from Argonne and from Brookhaven
Moral: We want ~6 good spares at all times
Required flux: At least 6/year.
ConclusionsConclusions Historical median lifetime
About 11000 hours (1.4 years)
Need at least 6 good spares for stable operation
Longevity of 7835 power tubes has decreased since 1990Some indication (hope?) this has turned
around
Must get at least ~6 tubes/yr from Burle If lifetime is under 8000 hours?
• Then Burle needs to improve flux
