Transcript Decay Volume

NUMI
NuMI Prototype Horn
& Final Power Supply Testing
•Magnetic Field Measurement
•Vibration Measurement
•Pulse-to-pulse stability
•Fatigue Lifetime Measurement
•DeBugs
(Description of Horn for reference)
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 1
NUMI
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 2
Magnetic Horn
General Design Features
Outer Conductor
B
p+
I
Stripline
Inner Conductor
Spray Nozzle
Focus p+ toward detector
•
•
•
•
•
•
Large toroidal magnetic field
Requires large current, 200 kAmp
Thin inner conductor, to minimize p+ absorption
Water spray cooling on inner conductor
Most challenging devices in beam design
Prototype test 1999-2000 to check design
Insulating Ring
Drain
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Horn Fabrication
Precision Welding
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 3
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Prototype Horn at Test Stand
upstream bell endcap
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 4
Features:
Anodize
outer conductor
(corrosion,
insulation)
Nickel plate
inner conductor
(corrosion,
fatigue)
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Horn Power Supply
Capacitor Bank + SCRs
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 5
Moves as single
11 ton unit
Other side
looks identical
Supplies 205 kA
to two horns
in series
Variable
2 ms to 5 ms
half-sin-wave
pulse width
1.87 second
repetition rate
120 7.5mF caps.
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Horn Power Supply
SCRs
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 6
SCRs
(3 of 12)
Stripline
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Horn Power Supply
SCRs
Charging supply and
controls/interlock rack
Second charging supply
added in series for
some cap-bank and
pulse-width combos
Now using one supply
at 860 Volts max. output
Problem during operation:
on circuit with diodes
to protect supply from
cap. bank back-feed in
case of fault – had to
use higher rating
component
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 7
NUMI
Horn Field Measurement
Main horn field between conductors
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 8
Field between conductors:
a 1/R as expected
very symmetrical
agrees within meas. error with current
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Horn Field Measurement
in ‘field-free’ region through center of horn
2% F/N criterion on flux in M.E. beam
(approximately scaled to 0.85 ms
test pulse from 2.6 ms operational pulse)
Measurement with probe
moving along horn axis
Error or fringe field in “field-free”
region down center of horn is so small
that no correction should need to be put
into the Monte Carlo.
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 9
NUMI
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 10
NuMI Horn 1
Vibration Measurements
Why
-Confirm ANSYS modeling so believable horn lifetime estimation.
-Horn resonances driven by transmission line, ground vibrations, etc.?
-Archival data useful if have a stress/fatigue failure
How
-Use “laser” non-contact absolute position sensor; eclipseometer.
Bandwidth ~ 20kHz. Sensitivity ~ 0.1 nanometer.
Measure at upstream inner cond. bell, 205 kA, 850 sec half-cycle, 1.9 sec rep rate.
Resonances described by a linear model
Resonance
Freq. (Hz)
1287
1175
188
168
163
Relative
Amplitude
-1.0
-1.0
0.05
- 0.16
0.16
-0.30
Decay
Const. (sec)
0.01
0.01
1.0
0.6
0.6
0.2
x = Ai sin(it) exp(-t/i)
Source
Horn Innerconductor
Horn Innerconductor
Transmission Line
Transmission Line
Transmission Line
Horn Thermal
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NuMI Horn 1
Vibration Measurement on Horn Bell Endcap
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 11
(ANSYS gives 71 m)
DATA
6 m
55 m
DATA
1.17 kHz (ANSYS 1.19 kHz)
Linear Model
0.03 sec
Linear Model
2 sec
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Pulse-to-pulse Stability
peak current and field monitor
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 12
Bdot coil
field
monitor
(sensitive to
water temp)
I1: Current in
Stripline 1
1%
I2
I3
1%
I4
Initial warm up
about 14 hours of data
NUMI
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 13
6 million pulses
2/3 of a ‘NuMI Year’ on horn prototype
pulses at 200 kA
4,000,000
3,000,000
2,000,000
Water line fixture fracture
5,000,000
Production Power Supply,
2.7 ms pulse, 205 kA peak
Test Power Supply,
0.85 ms pulse
1,000,000
0
Mar- Apr- May- Jun97
97
97
97
Jul97
Aug- Aug- Sep- Oct- Nov- Dec- Jan- Feb- Mar97
97
97
97
97
97
98
98
98
Date
(Runs nights and weekends only)
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Metal Flakes in Horn
Specks of metal collected on ceramic insulator
at bottom of horn - appears to be Nickel
Parts of horn visible through ports,
both anodized O.C. and nickel plated I.C,
look like new – would have to disassemble
horn to locate source of flaking
No operational problem noted yet,
but indicates water filter important
to prevent possible clogged spray nozzles
In horn, under water
Some flakes removed
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 14
NUMI
Lesson from Prototype
Water line
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 15
A water line overstressed
a feedthrough, which
cracked and allowed
a drip to develop
(The slow leak would not
have been fatal to a
horn in the NuMI
beamline)
Have modified the design
Old water tube
New strain-relieved
water tube
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Horn and Stripline
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 16
Afterthought:
Unistrut brace
between striplines
was added to reduce
vibration.
Brace cracked,
has been removed.
More noise without
brace, but vibration
of horn only
marginally affected
(Temporary
temperature
probe)
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Summary of Test
Minor troubles encountered
Redesign water line
Beef up charging supply snubber circuit
Very successful test:
Horn has taken 6 million pulses without breaking
Magnetic field looks great
Vibration matches expectations
Power Supply stability is good
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 17
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General Horn System
Parameters
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 18
Parameter
Horn 1
Neck Radius (cm)
0.9
Wall Thickness, Neck (mm)
4.5
Outer Conductor Radius to i.d. (cm)
14.9
Inductance (nH)
685-690
Resistance (µΩ)
208 (meas.)
Average Power from Current Pulse (kW)
17.0
Power Flux at Neck (W/cm2)
14.5
Temperature Rise at Neck (oC)
22.8
* Note: Above heat load numbers are from original design pulse
width of 5.2 msec
Horn 2
3.9
5.0
32.3
~457
<112
<7.5
<4.7
<7.1
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Mechanical Loading and Analysis
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 19
Mechanical Loading of Horn is the Result of :
- Current pulse thermal expansion from resistive heating (peak at the
end of the pulse)
- Magnetic forces (peak at the mid-pulse)
- Beam heating from particle interaction in material
Inner conductor resistive heating
Inner conductor beam energy deposition
Outer conductor beam energy deposition
Horn 1
Horn 2
17 kW
kW
14.5 kW
(1” thick)
<7.5 kW
0.4 kW
5.4 kW
(1” thick)
* Note: Above numbers from original design pulse width of 5.2 msec
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Mechanical Loading and Analysis
Areas of Highest Mechanical Loading
Values for 5.2 msec Pulse Width
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 20
• US end cap: minimum stress before pulse is -1030 psi; maximum
stress at mid-pulse is -9020 psi; mean stress is -5025 psi with an
alternating stress of 3995 psi; Stress ratio R=0.11
• Under the above calculated stress levels, allowable maximum stress for
107 cycles at endcap is 26.5 ksi resulting in fatigue safety factor of 2.9
• Neck of horn: stress at mid-pulse is +4351 psi; stress at end of pulse is
-3742 psi; mean stress is 304 psi with alternating stress 4047 psi;
Stress ratio R = -0.86 (Note: Negative value of R results in lower value
of fatigue stress limit)
• Under the above calculated stress levels, allowable maximum stress for
107 cycles at neck is 15.3 ksi resulting in fatigue safety factor of 3.5
• Stress in conductor weldment regions is very low (<<4 kpsi)
* Fatigue data from Aerospace Structural Metals Handbook
NUMI
Corrosion Considerations
Factors Affecting Fatigue Life
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 21
• Moisture reduces fatigue strength
– For R = -1, smooth specimens, ambient
temperature:
• N=108 cycles in river water,
• N=107 cycles in sea water,
smax= 6 ksi
smax~ 6 ksi
– Hard to interpret this data point
• N=5*107 cycles in air,
smax= 17 ksi
– The above data is motivation for utilizing
corrosion/encapsulating barrier layer over
aluminum substrate
NUMI
Horn
Corrosion Barrier Layer
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 22
• I.C.: Electroless nickel: reasonable corrosion barrier properties, nondielectric, more expensive, limited vendor base with large tank capacity
– Conducted fatigue test of nickel coated aluminum samples at the 107 fatigue
limit and compared results with equivalent non-coated aluminum specimens:
coated samples survived 1.7x 107 cycles, non-coated samples failed at 0.6x
107 cycles
– Use high phosphorus electroless nickel (0.0005” - 0.0007” thick) on inner
conductor and conductor supports
• O.C.: Anodizing: best solution for lower stress thick cross-section areas
Type III (hard coat sulfuric acid, 0.0023”), Rc 60-65, dielectric strength of
~800 V/mil
– Type III hardcoat anodize is selected for outer conductor and thick lead in
portion of inner conductor; not suitable for thinner/higher stress areas of
inner conductor due to approximate 60% reduction of fatigue strength
– Provides extra protection against I.C. to O.C. short circuit
NUMI
Horn Fabrication
Precision Welding
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 23
•Single pass, full penetration CNC weld is required to minimizing conductor
distortion, assure repeatability, and control internal weld porosity
• Proper cleaning, handling, fixtures, and weld parameters are crucial to minimize
conductor distortion and internal weld porosity
NuMI approached welding solution via parallel paths
1) Identify vendor base to subcontract critical horn conductor welding
- Vendor base for CNC TIG welding extremely limited and expensive; less
flexible fabrication path than in-house
- Prototype horn 1 fabricated in this manner using Sciaky as prime contractor,
ANL as subcontractor
2) Investigate the development of welding capability in-house
- Have specified, benchmarked, purchased, and commissioned a Jetline fully
automated TIG welding system for producing controlled conductor weldments
- System installed at MI-8 horn facility
- Long term solution for welding 4 initial horns (production and spare horn 1
and horn 2)
NUMI
Technical Progress
Prototype Horn 1 Design Summary
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 24
Conductor Fabrication
•Inner conductor fabricated from 6061-T6 billet per QQA 200/8
•Relatively good strength (UTS ~ 45 ksi, YS ~ 40 ksi, R=-1 FS ~ 16 ksi)
•Available in variety of sizes and shapes
•Welds readily
•Relatively good corrosion resistance
•All prototype horn inner conductor parts CNC machined by Medco to tolerances
better than ~ 0.002”
•Inner conductor welding complete - CNC TIG - Overall tolerances held to ±0.010”
over 133.375” length (straightness and radial deviation from ideal)
•Outer conductor overall tolerances better than ±0.010”
•Outer conductor anodized, inner conductor uses electroless Ni coating
•Stripline contact surfaces use 0.0005” silver brush plating
NUMI
Prototype Horn 1 Design Summary
NuMI Horn Testing
Jim Hylen (FNAL)
NBI02 March 13, 2002
Page 25
•Water Seals
- Total of 64 water seals in horn
- Utilize EVAC aluminum delta seals on KF style flange
•Bolted Connections
- Utilize TimeSert threaded inserts, pullout exceeds 9600 lb. on 3/8” insert
- As a reference, maximum end wall reaction is approximately 4270 lb.
•Current Contact Surfaces
- Current surfaces have 32 µin finish, 0.0003”-0.0005” silver plate finish
- Interface clamping pressure exceeds 1400 psi
- As reference, lithium lens secondary contact lead is 5.01 in2 for 6285 Arms;
Prototype horn 1 contact area is 9.2 in2 for 7250 Arms.
•Corrosion/Erosion Control
- Outer conductor and thick lead in section of inner conductor employs 0.0023”
thick Type III hard coat anodize followed by mid-temp nickel seal
- Inner conductor utilizes 0.0007” thick high phosphorus electroless nickel
•Inner Conductor Spider Support Columns
- Design has been experimentally tested to 36 million cycles at defections of ±0.031”
with 80 lbs. axial preload with no failures