stewart shen [email protected] april 20, 2006 ucrl-pres-xxxx lcls x-ray absorber richard bionta, keith...
Post on 20-Dec-2015
215 views
TRANSCRIPT
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
LCLS X-Ray Absorber
Richard Bionta, Keith Kishiyama, Donn McMahon, Marty RoebenDimitri Ryutov, John Trent and
Stewart Shen
This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under Contract No. W-7405-Eng-48.
LCLS FAC Meeting
April 20, 2006
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Contents
• Introduction • Requirements• General Concept
• Gas Attenuator Pressure System Conceptual Design • Passive Pumping Design• Performance Analysis• Gas Attenuator Prototype
• Solid Attenuation & Actuator Testing • Instrumentation and Control • Attenuator Subsystem Schedule• Summary
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Category Subject Requirement General Energy Range FEL photon energy from 826.5 eV to 8265 eV.
Attenuation Range Up to 4 orders of magnitude
Accuracy & Repeatability Stable, reproducible attenuation for repeated FEL shots. Within 1.5% for attenuation factor of 10. Within 5% for attenuation factor of 10,000. Uniformity of attenuation over transverse dimension of the FEL beam is better than 1 % for all attenuation levels.
Mechanical-Vacuum Design
Consistent with PRD 1.5-002, “XTOD Mechanical-Vacuum Systems.”
Discrete levels for solid attenuation
At least 3 steps for every decade of attenuation, up to 104.
Space Consistent with FEE environment for installation, operation and maintenance
Optics Aperture –“in-operation” permit un-obstructed passage of the full transverse extent (4σ) of the FEL photon beam
Aperture – “fully open” permit un-obstructed passage of the full transverse extent of the projected radiation field from the undulator, limited only by components upstream of the Front End Enclosure.
Material Selection limit the effect of scattered radiation and degradation of FEL beam transverse coherence, consistent with requirements of anticipated LCLS experiments.
Control System Fully-remote-controlled safe operation
Level change time-Solid Some seconds
Level change time-gas Several minutes.
Updated Physics Requirements*
* LCLS-PRD-1.5-003 “Physics Requirements for the XTOD Attenuator System”, 3/15/2006
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Attenuator envelope is 10 meters, with 6 m at high pressure
Fast Valve
X-ray Slit
Ion Chamber
Attenuator
Fixed Mask
Diagnostics
Offset Mirrors
Baseline Plan: Use 6 meters of N2 gas for EFEL < 2 keVUse solid Be blocks for EFEL > 2 keV
* For a transmission of 10-4
Use Gas
Use Solids
Maximum N2 pressure
20 Torr
Maximum Be
thickness 5.7 cm
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Nitrogen Pressure Requirements
Required N2 Pressure for Different Attenuation600 cm
0
5
10
15
20
0.0001 0.001 0.01 0.1 1
Attenuation Factor
N2
Pre
ssur
e (T
orr)
1.95 KeV
1 KeV
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Attenuator Conceptual Configuration
6 meter long, high pressure N2
section3 Differential
pumping sections separated by 3 mm apertures
N2 Gas inlet
3 mm diameter holes in Be disks
allow 880 m (FWHM), 827 eV
FEL to pass unobstructed
Solid Be attenuators are inserted in the high-pressure
section
N2 boil-off (surface)
Flow restrictor
Green line carries
exhaust to surface
3 mm Apertures in Transition Stages with Bellows to allow transverse positioning of opening in window
Be disk on gate valve survives FEL hits. Disks are transparent to high energy spontaneous, allowing alignment of hole using
WFOVDI camera in FEE. Gate valve removes window when gas attenuator not in use and for ease of alignment.
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Alignment concept using direct imager
20 Torr 0.7 Torr
0.7 Torr
Gas AttenuatorGas Detector 1
Gas Detector 2
~10-6 Torr
~10-6 Torr
6 m10 cm
10 cm2 m 2 m
1.5 m 1.5 m
WFOV Direct Imager
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Open valves to align sections
20 Torr 0.7 Torr
0.7 Torr
Gas AttenuatorGas Detector 1
Gas Detector 2
~10-6 Torr
6 m10 cm
10 cm2 m 2 m
1.5 m 1.5 m
WFOV Direct Imager
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
10 cm
1 window 1 window with Ta ring 3 windows with Ta rings
Low energy spontaneous through attenuator windows(40 mm diameter x 1 mm thick with 3 mm diameter hole through center)
10 c
m
3 mm hole may be hard to see (limited by simulation statistics) but Ta rings allow easy identification of hole position
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
All valves open
3 valves closed4.6 mR + 6 mm misalignment
3 valves closed0.46 mR + 300 m
misalignment
Direct imager image of saturated low energy FEL + Spontaneous
With this method it is easy to locate the FEL and systematically align the apertures with the FEL wherever it is located
10-m 6 port 3-mm Aperture720 L/s Qi = 0 sccmPump Down
Base Pressure
0 150 300 450 600 750 9001 10
81 10
71 10
61 10
51 10
41 10
30.01
0.1
1
10
100
1 103
ChamberPort-2Port-5Port-7
DP-Vacuum
Time (s)
Torr
• Final outgassing rates of 10-9 T-L/s-cm2 is assumed• Scroll Pump Speed vs Pressure is modeled• Turbo Pump Speed vs Pressure is modeled
System Pump down Performance
0 50 100 1501 10
8
1 107
1 106
1 105
1 104
1 103
0.01
0.1
1
10
100
ChamberPort-2Port-5Port-7
DP-Vacuum
Time (s)
Torr
Chamber pressure log scale
18.8 Torr
4x10-7 Torr
Vacuum to full pressure with = 50 seconds
0 50 100 1500
5
10
15
20P1- Gas Chamber
Time (s)
Torr
t 0 .01 20
0 4 8 12 16 200
25
50
75
100Nitrogen Gas Flow
Time
T-L
/s Qi t( )
t
These calculations show 20 Torr achievable in central chamber with 3 mm holes…
Inlet N2 flow Qi = 5053 sccm
Chamber pressure linear scale
…while pressure in external beam pipe remains low.
Full Scale System has reasonable flow rates and pumping requirements
Parameter Unit Value Configuration Passive 6-port B Total Length m 10 Gas Chamber Length m 6.0 Diameter m 0.15 Port 2 &3 Length m 1 Diameter m 0.15 Port 4 &5 Length m 0.5 Diameter m 0.125 Port 6 &7 Length m 0.5 Diameter m 0.125 Total Equivalent Combined Pumping Speed (turbo+scroll)
L/s 720
Gas N2 Chamber Pressure for 104 Attenuation
Torr 19
Max Gas Flow sccm 5400 1st Port Pressure (V2) Torr 1.8 Last Port Pressure (V7) Torr 4.2x10-7
Attenuator Risks and Mitigations
• Pressure calculations are wrong, or system is not stable (pumping, temperature, flow)• Testing underway in prototype, pressure ok, stability, temperature
TBD• Accuracy & Repeatability Unachievable
• 1% attenuation accuracy & repeatability is difficult to achieve at attenuation factors above 102 because of the very high precision in gas uniformity required. The requirement has been relaxed to 5%. Accuracy at this level requires calibration.
• Other sources of uncertainty (temperature, gas purity, absorption coefficient), Stresses on Be Diaphragm, Erosion of Be Diaphragm• Calculations show these are not a problem
• Heating of the gas by FEL could be an issue• Requires more study
Attenuator Risks and Mitigations (cont.)
• Contribution of the transition stages to uncertainties in the attenuation• Under study, smaller transition better
• 3 mm aperture not large enough to accommodate FEL spatial envelope• Larger aperture would limit achievable pressures
• Corrosion of the Be by the N2 gas or ions• This could be a serious problem but is hard to quantify
Ar could be substituted for N2 to overcome some risks*
Gas Pressure (600 cm)
0
5
10
15
20
25
0 0.5 1 1.5 2 2.5
Photon Energy (KeV)
Pre
ssur
e (T
orr)
Ar
N2
Pressure of 600 cm of Ar and N2 for 104 Attenuation
Ar requires less pressure so could accommodate slightly larger aperturesAr will not corrode Be
*LCLS-TN-06-1 "The Physics Analysis of a Gas Attenuator with Argon as a Working Gas." UCRL-TR-217980 (January 2006) D.D. Ryutov, R.M. Bionta, M.A. McKernan, S. Shen, J.W. Trent,
Ar could work up to 8 keV at 60 Torr
Gas Pressure (600 cm)
0
10
20
30
40
50
60
0 1 2 3 4 5 6 7 8
Photon Energy (KeV)
Pre
ssu
re (
To
rr)
Ar
N2
Ar at 60 Torr would eliminate the need for the solid attenuator, but the absorption edge at 3 keV and added safety concerns about heavy
gasses, makes Ar less than ideal. We keep Ar as a backup option and will test its use in the prototype.
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Prototype Gas Attenuator Has Been Completed Configuration
Objectives
Phase 1
Demonstrate stable control of gas chamber pressure (N2 & Ar)
Validate the vacuum design for intermediate flow
Verify mechanical & thermal stability
Phase 2
To measure the effect of aperture-nozzle geometries.
Integration with Solid
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Prototype System is one-half of the full LCLS gas attenuator
Gas Chamber
Port 1,2,3
Scroll
Turbo
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Preliminary Test Results- N2
Gas Attenuator Pressure
(Measurement vs Modeling)
1.0E-07
1.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
1.0E+01
0.00 20.00 40.00 60.00 80.00
Chamber Pressure P1 (Torr)
Sta
ge P
ress
ure
(T
orr)
P2
P3
P4
P2/Cal
P3/Cal
P4/Cal
Pump ArrangementV2 2 10 L/s ScrollV3 1 600 L/s TurboV4 1 70 L/s Turbo
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Preliminary Results- N2 -3rd Stage
Gas Attenuator Pressure (Measurement vs Modeling)
1.0E-07
1.0E-06
1.0E-05
1.0E-04
0.00 10.00 20.00 30.00 40.00 50.00
Chamber Pressure P1 (Torr)
Sta
ge P
ress
ure
(T
orr)
P2
P3
P4
P2/Cal
P3/Cal
P4/Cal
Good Agreement with Calculation
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Prototype Preliminary Results Summary
• Computer Model Bench Marked and Validated
Gas Flow (input flow, conductance)
Pump Performance
Pressure Distribution
• Met 20-Torr Design Goals
• Stable Short-Term Operation Up to 50 Torr Nitrogen
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator Concept Overview
• 128 attenuation levels• Seven beryllium slides
• 0.375, 0.75, 1.5, 3, 6, 12, and 24 mm thick
• Gives 0 to 47.625 mm in 0.375 mm increments
• Up to 20,000x attenuation of 8.26 keV x-rays
• Pneumatically actuated
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator Features
• Repeatable within 0.1% of attenuation level• Fast changes – couple seconds• Safe - Only Be can intersect FEL (holder is open on
end)• Safe - Actuators fail in with internal spring• Verified in place – micro-switches on actuator• Takes up no space in Z (it’s inside gas cell)• Be slides polished to optical finish
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Front View – Attenuating
Pneumatic Actuator
Attenuator Block Holder
Custom Vacuum Vessel
Adapter Flange
Attenuator Block
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Front View – Open
Spontaneous Radiation Clear Aperture
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
How Solid and Gas Work Together
• For 8.26 keV x-rays the range of the gas attenuation with Nitrogen at 0 to 20 Torr is 100% to 88.1% transmission (0 to 12% attenuation)
• The thinnest solid attenuator (0.375 mm) at 8.26 keV provides 92.5% transmission (8% attenuation)
• Overlap means gas fills in between solid levels – very fine resolution and large range
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator will be in Gas Attenuator
Solid Attenuator
(Upstream end preferred to minimize effect of Compton scattering on downstream diagnostics)
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator Actuator Testing
• ObjectiveTo determine the solid rotation angle, mainly about vertical axis
• ActuatorHuntington UHV compatible pneumatic actuator; model L-2271-4-LL-2D-SM-EX, with spring to extend
• SetupUse custom test stand and representative test block. Cycle actuator and measure using CMM
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator Actuator Prototype
• Measured angular repeatability of face of test block
• Used Coordinate Measuring Machine to determine precise location of face over 10 cycles
Actuator
Test Block
CMM Probe
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Solid Attenuator Actuator Prototype Results
• Actuator repeats 11 times better than required• Repeats within 0.2 degrees• Requirement is 2.2 degrees for 5% repeatability
at highest attenuation level
• Overall attenuation will repeat within 0.1% at the highest attenuation level due to angular repeatability• Requirement is 5% repeatability
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Plan for Beryllium Procurement
• Make all attenuator slides from one batch• Baseline Be has 200 ppm Fe• One typical batch can yield two sets of slides
• Test attenuation length of Be• Make Be slide of well measured thickness from
batch• Measure attenuation length of Be batch sample
slide using x-rays
We plan to use polished O-30H Be for the solid attenuator blocks
O - 30H OPTICAL GRADE BERYLLIUM
Effective Date: April 30, 1998 1. Scope
1.1. This specification establishes the material requirements for an optical grade of hot isostatically pressed (HIP) beryllium, suitable for low scatter optical applications which is designated O-30H.
This is a high density, high purity, low oxide material with good polishing
characteristics. It is more isotropic than other grades of beryllium with 45,000 psi typical yield strength and 4,000 psi typical micro yield strength.
2. Chemical Composition
2.1. The chemical composition shall conform to the following:
Beryllium Assay, % minimum (1) 99.0 Beryllium Oxide, % maximum (2) 0.50 Aluminum, % maximum (3) 0.07 Carbon, % maximum (4) 0.12 Iron, % maximum (3) 0.12 Magnesium, % maximum (3) 0.07 Silicon, % maximum (3) 0.07 Other Metallic Impurities, each, % maximum (3) 0.04
O-30H is the best Be for for polishing minimizing coherence effects
2 sets of solid attenuator blocks can be fabricated for ~$30K (materials, cutting, and polishing)
We invite you to visit our website at www.axsys.com for additional information regarding Axsys Technologies capabilities. If you have questions, please contact Customer Support or your Axsys Regional Sales Manager.
CS-F 006 2/04
To: LLNL From: Norman Love Mr. Mark McKernan
7000 East Ave. Livermore, CA 94550
Axsys Technologies, Inc. 6717 Alabama Hwy. 157 Cullman, AL 35057
Phone: (925) 423-1488 Phone: (256) 737-5248 Fax: Fax: (256) 739-8298
E-Mail: [email protected] E-Mail: [email protected]
Cust Ref # Axsys File # NL05-0740
Sales Manager: Al Mejia
Item Quantity Description Unit Price NRE Delivery
1 32 P/N NL05-0724, Be Optical Coupon $1,118.00 $1,044.00 ARO, 19 weeks
Terms: Net 30 Days F.O.B.: Cullman, Alabama Quote Validity: 30 Days
Notes: 1. Quoting 0-30H Beryllium. Quote assumes no optical overcoat. Quoting to run in one lot.
Export Compliance: Export of parts listed on this quote, commodities, defense articles, and/or technical data is subject to U.S. export control laws and regulations including, but not limited to, the International Traffic in Arms Regulations (ITAR) (22 CFR 120-130) or the Export Administration Regulations (EAR) (15 CFR 730-774). It is Axsys’ understanding that if the above products are to be resold or exported, your company will comply with all applicable U.S. export control laws and regulations and, if applicable, obtain any and all necessary export licenses. Price is based upon specified quantities and delivery schedule. Changes may result in prices being renegotiated. Axsys Technologies requests that a drawing revision is accompanied by an engineering change order clearly stating the was/is condition. Should this not be available, Axsys reserves the right to charge a review fee of $300 to create the change request and documentation.
QUOTATION
Date: 9/20/05
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Attenuator I&C Approach
Ethernet
IOC
Gauge ControllerGauge Controller
Pressure ControllerPressure Controller
Turbo ControllerTurbo Controller
Vacuum setpoints and alarms
Gas Attenuator
Gate Valves
Turbo Pump
Baratron, Stabil Ion
Gate Valve I/O
Eth
ern
et In
terf
ace
1756
EN
ET
1794
AE
NT
Flex I/O
EtherNet/IP
Scroll PumpScroll pump control
Vacuum Interlocks
Ser
ial i
nte
rfac
e
OPIPC/Linux
Co
ntr
ol L
og
ix
0 - 5 vdc
RS-232
Magnetic StarterMagnetic Starter
PC/WindowsRSLogix software
OPIPC/Linux
RS-232
D/A
con
vete
r
MKS 649
The control system for the attenuator will consist of a PLC that will be connected via a network to the global control system, EPICS
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Fault Tree with Control – Example 1
System Failure or Condition
Probability Symptom PLC Response/Interlock
Scroll and Turbo Pumps
Scroll pump head failure
Low/med - failures are usually due to lack of periodic maintenance (every 10,000 hours)
Low base pressure Low pump speed
Pirani gauge monitoring foreline pressure or pirani or baratron gauge monitoring ports 2 & 3 PLC interlock will shutdown scroll pump PLC interlock will shutdown turbo PLC interlock will close turbo gate valve PLC interlock will shutdown gas flow PLC sends scroll pump fault message to EPICS
Scroll pump motor failure
Low - motor bearing or winding failure uncommon
High motor current or windings open or short
Motor control circuit (or circuit breaker) will shutdown the scroll pump and send a fault signal to the PLC PLC interlock will shutdown turbo PLC interlock will close turbo gate valve PLC interlock will shutdown gas flow PLC sends scroll pump fault message to EPICS
Scroll pump gas load too high
med - vacuum system leak or contamination or gas flow too high in gas attenuator chamber
High motor current
System will not pump down, PLC will timeout, stop pump, send timeout message to EPICS Scroll pump will overheat, motor control circuit will shutdown the scroll pump and send fault signal to PLC PLC interlock will shutdown gas flow PLC interlock will shutdown turbo PLC interlock will close turbo gate valve to protect scroll pump PLC sends scroll pump fault message to EPICS
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Fault Tree with Control – Example 2System Failure or
Condition Probability Symptom PLC Response/Interlock
Scroll and Turbo Pumps (Cont.)
Turbo pump bearing failure
Low - modern ceramic bearings are very reliable
High motor temp High motor current
Turbo controller will provide safe shutdown and send fault signal to PLC PLC interlock will shutdown gas flow PLC interlock will close turbo gate valve PLC sends turbo fault message to EPICS
Turbo rotor crash Low - Unless turbo ingests foreign object or is subject to multiple atmospheric vents while operating at full speed
Sudden drop in RPMs
Turbo controller will shutdown pump and send fault signal to PLC PLC interlock will shutdown gas flow PLC interlock will close turbo gate valve PLC sends turbo fault message to EPICS
Turbo gas load too high
Low/med - vacuum system leak or contamination or gas flow too high in gas attenuator chamber
High motor current High motor temp Low RPMs
Turbo controller will provide safe shutdown and send fault signal to PLC PLC interlock will shutdown gas flow PLC interlock will close turbo gate valve to protect turbo PLC sends turbo fault message to EPICS
Electronic pressure controller
Gas supply empty or pressure too low to regulate
Low/med – pressure transducer on supply will alert when supply is too low
Pressure drop in gas attenuator chamber
Pressure transducer will provide signal to PLC PLC interlock will alert operators that supply is low PLC interlock to MPS will dump beam if pressure is critically low
Malfunction in electronic pressure controller
Low – unit is widely used in semiconductor industry
Pressure in attenuator unstable
Baratrons monitoring pressure in attenuator will have an interlock window around pressure setpoint PLC interlock to MPS will dump beam if pressure is outside setpoint window
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
XTOD Attenuator Subsystem Schedule
1. System Concept Review (4/13/06)2. Prototype Testing Results (5/06)3. ESD (6/06)4. Preliminary Design Review (12/06)5. Final Design Review (2/07)6. Procurement (6/07)7. Assemble/Test (8/07)8. FEE Beneficial Occupancy (8/07)
Stewart Shen
April 20, 2006 UCRL-PRES-xxxx
Summary
• Conceptual design meets requirements• Design uses combination of gas and solid materials• Computer gas flow model has been calibrated and is a powerful design tool
• Prototype testing is producing useful data• Gas flow & pressure management is under control
• Project is on schedule to meet current baseline