LRS Micro-g LaCoste FG5 User manual

Table of Figures
1. CONCEPT AND HISTORY OF THE FG5.................................................. 1-1
1.1. The FG5 Absolute Gravimeter................................................................................................... 1-1
1.2. HISTORY...................................................................................................................................... 1-1
1.3. FG5 Design Features .................................................................................................................... 1-2
2. DESIGN: COMPONENTS AND FUNCTION ............................................. 2-1
2.1. The Dropping Chamber .............................................................................................................. 2-2
2.1.1. CART/DRAG-FREE CHAMBER........................................................................................... 2-4
2.1.2. TEST MASS ............................................................................................................................ 2-5
2.1.3. DRIVE MECHANISM ............................................................................................................ 2-6
2.1.4. SERVICE RING ...................................................................................................................... 2-6
2.1.5. VIEWING PORT..................................................................................................................... 2-7
2.1.6. THE DROP .............................................................................................................................. 2-7
2.2. The Interferometer Base.............................................................................................................. 2-9
2.2.1. LASER..................................................................................................................................... 2-9
2.2.2. OPTICS AND BEAM PATH .................................................................................................. 2-9
2.3. The Superspring......................................................................................................................... 2-12
2.3.1. SUPERSPRING MASS ......................................................................................................... 2-12
2.3.2. SPHERE DETECTOR SYSTEM .......................................................................................... 2-12
2.4. The System Controller ............................................................................................................... 2-14
2.4.1. REQUIRED HARDWARE ................................................................................................... 2-15
2.4.2. OPTIONAL HARDWARE.................................................................................................... 2-15
2.4.3. SOFTWARE .......................................................................................................................... 2-15
2.5. Electronics................................................................................................................................... 2-15
2.5.1. TIMING SYSTEM ................................................................................................................ 2-15
2.5.2. DROPPER CONTROLLER .................................................................................................. 2-17
2.5.3. SUPERSPRING CONTROLLER.......................................................................................... 2-18
2.5.4. LASER CONTROLLER........................................................................................................ 2-18
2.5.5. POWER SUPPLIES............................................................................................................... 2-19
2.5.6. OPTIONAL SYSTEMS......................................................................................................... 2-19
2.5.6.1. ENVIRONMENTAL SENSORS....................................................................................... 2-19
2.5.6.2. ROTATION MONITOR.................................................................................................... 2-20
3. HOW TO SET UP AND RUN THE FG5..................................................... 3-1
3.1. Setting Up the FG5 ....................................................................................................................... 3-1
3.1.1. ELECTRONICS CASE ........................................................................................................... 3-1
3.1.1.1. Model ML-1 Laser:.............................................................................................................. 3-2
3.1.1.1.1. Warm Up........................................................................................................................ 3-2
3.1.1.1.2. Operation .......................................................................................................................3-2
3.1.1.2. WEO Model 100 Laser ........................................................................................................ 3-3
3.1.2. SUPERSPRING ....................................................................................................................... 3-5
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Table of Figures
3.1.3. INTERFEROMETER...............................................................................................................3-6
3.1.4. DROPPING CHAMBER TRIPOD ..........................................................................................3-6
3.1.5. ION PUMP ...............................................................................................................................3-7
3.1.6. LEVELING THE DROPPING CHAMBER ............................................................................3-8
3.1.7. CABLE CONNECTIONS ........................................................................................................3-9
3.1.8. THE SUPERSPRING.............................................................................................................3-11
3.1.8.1. TRAVEL LOCK.................................................................................................................3-12
3.1.8.2. SUPERSPRING ZERO-POSITIONING............................................................................3-12
3.1.9. BEAM VERTICALITY .........................................................................................................3-13
3.1.10. FRINGE OPTIMIZING..........................................................................................................3-14
3.2. Running the FG5.........................................................................................................................3-17
3.2.1. SYSTEM CONTROLLER .....................................................................................................3-17
3.2.2. DROPPER CONTROLLER...................................................................................................3-17
3.2.3. PROGRAM SETUP ...............................................................................................................3-17
3.3. Shutting Down the FG5 ..............................................................................................................3-18
3.3.1. COMPUTER ..........................................................................................................................3-18
3.3.2. SUPERSPRING......................................................................................................................3-18
3.3.3. INTERFEROMETER.............................................................................................................3-19
3.3.3.1. OPTION 1: Model ML-1 Laser. ........................................................................................ 3-19
3.3.3.2. OPTION 2: WEO Model 100 Laser ...................................................................................3-19
3.3.4. DROPPING CHAMBER........................................................................................................3-19
3.3.5. POWER ..................................................................................................................................3-19
3.4. Disassembling and Packing the FG5.........................................................................................3-20
3.4.1. ELECTRONICS .....................................................................................................................3-20
3.4.2. SYSTEM CONTROLLER .....................................................................................................3-20
3.4.3. ROTATION MONITOR (IF INCLUDED)...........................................................................3-21
3.4.4. DROPPING CHAMBER........................................................................................................3-22
3.4.5. DROPPING CHAMBER TRIPOD ........................................................................................3-22
3.4.6. INTERFEROMETER BASE.................................................................................................. 3-22
3.4.7. SUPERSPRING......................................................................................................................3-23
3.4.8. TURBO PUMP (IF USED) ....................................................................................................3-23
4. ADJUSTMENT AND MAINTENANCE........................................................4-1
4.1. The Dropping Chamber...............................................................................................................4-1
4.1.1. REPLACEMENTS AND ADJUSTMENTS ............................................................................4-1
4.1.1.1. Removing The Dropping Chamber Cover............................................................................4-1
4.1.1.2. Replacing the Dropping Chamber Cover..............................................................................4-2
4.1.1.3. Replacing the Drive Belt ......................................................................................................4-4
4.1.1.4. Adjusting the Drive Belt Tension .........................................................................................4-5
4.1.1.5. Replacing the Ferrofluidic Vacuum Feedthrough.................................................................4-5
4.1.1.6. Replacing the V-Plate ...........................................................................................................4-6
4.1.1.7. Replacing the Linear Bearings..............................................................................................4-7
4.1.1.8. Replacing the Shaft Bearings—Drive Pulley........................................................................4-8
4.1.1.9. Replacing the Shaft Bearings—Top Pulley ..........................................................................4-9
4.1.1.10. Replacing the Rotary Shaft Encoder...................................................................................4-9
4.1.1.11. Pumping Down the Dropping Chamber ...........................................................................4-10
4.2. The Interferometer .....................................................................................................................4-10
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Table of Figures
4.2.1. ALIGNMENT........................................................................................................................ 4-10
4.3. The Superspring......................................................................................................................... 4-13
4.3.1. REPLACEMENTS AND ADJUSTMENTS.......................................................................... 4-13
4.3.1.1. Removing the Superspring Cover ...................................................................................... 4-13
4.3.1.2. Removing the Service Ring................................................................................................ 4-13
4.3.1.3. Replacing the Coil (Linear Actuator)................................................................................. 4-14
4.3.1.4. The Mass Mainspring/Hanger............................................................................................ 4-15
4.3.1.5. Replacing the Flexures....................................................................................................... 4-15
4.3.1.6. Assembling the Superspring............................................................................................... 4-18
4.3.1.7. Replacing the Focus Lever Motor...................................................................................... 4-19
4.3.1.8. Adjusting the Micro-Switches............................................................................................ 4-19
4.3.1.9. The Aneroid Wafer Assembly............................................................................................ 4-19
4.3.1.10. The Delta Rods................................................................................................................. 4-20
4.4. Timing System and Data Acquisition....................................................................................... 4-21
4.4.1. TIMING ................................................................................................................................. 4-21
4.4.1.1. Avalanche Photo Diode Printed Circuit Board .................................................................. 4-23
4.4.1.2. APD Board and Photo Diode Supply Module.................................................................... 4-23
4.4.1.3. Rubidium Oscillator ........................................................................................................... 4-24
4.4.2. DATA ACQUISITION.......................................................................................................... 4-25
4.4.2.1. Computer Interface Cards .................................................................................................. 4-25
4.5. DROPPER CONTROLLER ..................................................................................................... 4-25
4.5.1. DROPPER CONTROL MODES ........................................................................................... 4-27
4.5.1.1. STANDBY.........................................................................................................................4-27
4.5.1.1.1. To Select ...................................................................................................................... 4-27
4.5.1.1.2. Function ....................................................................................................................... 4-27
4.5.1.1.3. To Deselect .................................................................................................................. 4-27
4.5.1.2. MANUAL ..........................................................................................................................4-27
4.5.1.2.1. To Select: ..................................................................................................................... 4-27
4.5.1.2.2. Function: ...................................................................................................................... 4-27
4.5.1.3. DROP................................................................................................................................. 4-27
4.5.1.3.1. To Select: ..................................................................................................................... 4-27
4.5.1.3.2. Function: ...................................................................................................................... 4-28
4.5.1.4. OSCILLATE...................................................................................................................... 4-28
4.5.1.4.1. To Select: ..................................................................................................................... 4-28
4.5.1.4.2. Function: ...................................................................................................................... 4-28
4.5.2. Analog Servo.......................................................................................................................... 4-28
4.5.2.1. Cart-Position ...................................................................................................................... 4-29
4.5.2.2. Cart Velocity ...................................................................................................................... 4-29
4.5.2.3. Sphere Servo ...................................................................................................................... 4-30
4.5.2.4. Active Sphere Servo........................................................................................................... 4-30
4.5.2.5. Feedforward Sphere Servo................................................................................................. 4-31
4.6. Superspring Controller .............................................................................................................. 4-31
4.6.1.1. SUPERSPRING CONNECTIONS .................................................................................... 4-31
4.6.1.2. MOTOR DRIVE SELECTION ......................................................................................... 4-33
4.6.1.2.1. OFF .............................................................................................................................. 4-33
4.6.1.2.2. AUTO .......................................................................................................................... 4-33
4.6.1.2.3. WINDOW.................................................................................................................... 4-33
4.6.1.2.4. REMOTE ..................................................................................................................... 4-33
4.6.1.2.5. MANUAL.................................................................................................................... 4-33
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Table of Figures
4.6.1.3. Active Servo .......................................................................................................................4-33
4.6.1.4. Coil Drive (Current Driver) ................................................................................................4-34
4.6.2. Maintenance Schedule............................................................................................................4-34
4.6.2.1. Annually .............................................................................................................................4-34
4.6.2.2. Semi-annually..................................................................................................................... 4-34
5. TROUBLESHOOTING ...............................................................................5-1
5.1. The FG5 System ............................................................................................................................5-1
5.2. System Problems ...........................................................................................................................5-2
5.2.1. DROPPING CHAMBER..........................................................................................................5-2
5.2.2. INTERFEROMETER AND LASER........................................................................................5-5
5.2.3. SUPERSPRING........................................................................................................................5-8
5.2.4. SYSTEM CONTROLLER .....................................................................................................5-10
5.2.5. ELECTRONICS .....................................................................................................................5-11
5.2.6. ENVIRONMENTAL SENSORS PACKAGE .......................................................................5-12
5.2.7. ROTATION MONITOR ........................................................................................................5-13
5.3. Gravity Site Selection..................................................................................................................5-14
5.3.1. GEOLOGIC STABILITY ......................................................................................................5-14
5.3.2. SITE STABILITY ..................................................................................................................5-14
5.3.3. ENVIRONMENTAL NOISE.................................................................................................5-14
5.3.4. TEMPERATURE STABILITY..............................................................................................5-14
5.4. AC POWER.................................................................................................................................5-15
6. SWITCHING THE AC POWER ..................................................................6-1
6.1. LASER ...........................................................................................................................................6-1
6.1.1. WEO Model 100 Laser.............................................................................................................6-1
6.1.2. ML-1 Laser...............................................................................................................................6-2
6.2. Portable Ion Pump Power Supply ...............................................................................................6-2
6.3. Computer.......................................................................................................................................6-2
7. PUMPING/BAKING THE CHAMBER ........................................................7-1
7.1. Choosing the Pumping Method....................................................................................................7-1
7.1.1. Cold Pumping the Chamber...................................................................................................... 7-1
7.1.2. Baking Out the Chamber ..........................................................................................................7-1
7.2. Connecting the Turbo Pump to the Dropping Chamber...........................................................7-2
7.3. Heating the Chamber....................................................................................................................7-3
7.4. Starting the Ion Pump ..................................................................................................................7-4
8. THE ROTATION MONITOR.......................................................................8-1
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Table of Figures
8.1. INSTALLATION ......................................................................................................................... 8-1
9. CHECKLISTS AND LOGS ........................................................................ 9-1
9.1. Switching the AC Power .............................................................................................................. 9-1
9.2. FG5 Setup...................................................................................................................................... 9-2
9.3. Dropping Chamber Pump Down and Bake-Out ....................................................................... 9-5
9.4. Dropping Chamber Maintenance ............................................................................................... 9-7
9.4.1. Removing Dropping Chamber Cover....................................................................................... 9-7
9.4.2. Replacing Dropping Chamber Cover....................................................................................... 9-7
9.4.3. Replacing Drive Belt................................................................................................................ 9-8
9.4.4. Adjusting Belt Tension ............................................................................................................ 9-9
9.4.5. Replacing Ferrofluidic Vacuum Feedthrough.......................................................................... 9-9
9.4.6. Replacing V-plate .................................................................................................................. 9-10
9.4.7. Replacing the Linear Bearings ............................................................................................... 9-11
9.4.8. Replacing Shaft Bearings (Drive Pulley) ............................................................................... 9-13
9.4.9. Replacing Shaft Bearings (Top Pulley).................................................................................. 9-14
9.4.10. Replacing Rotary Shaft Encoder ............................................................................................ 9-15
9.5. Interferometer Alignment.......................................................................................................... 9-16
9.6. Superspring Maintenance.......................................................................................................... 9-18
9.6.1. Removing Superspring Cover ................................................................................................ 9-18
9.6.2. Replacing Superspring Cover................................................................................................. 9-18
9.6.3. Removing Superspring Service Ring ..................................................................................... 9-19
9.6.4. Replacing Superspring Coil ................................................................................................... 9-19
9.6.5. Replacing Superspring Flexures............................................................................................. 9-20
9.6.6. Assembling Superspring ........................................................................................................ 9-22
9.6.7. Replacing Superspring Focus Lever Motor............................................................................ 9-25
9.6.8. Adjusting Superspring Micro-Switches ................................................................................. 9-26
9.7. Packing the FG5 ......................................................................................................................... 9-26
10. INDEX ........................................................................................................... 10-1
Figure 2-1 The FG5 System......................................................................................... 2-1
Figure 2-2 Front view of the dropping chamber ...................................................... 2-2
Figure 2-3 Side view of the dropping chamber ........................................................2-3
Figure 2-4 Front view of the cart/drag-free chamber..............................................2-4
Figure 2-5 Side view of the cart/drag-free chamber................................................2-5
Figure 2-6. Side view of the service ring................................................................... 2-6
Figure 2-7 Top view of the service ring. .................................................................... 2-7
Figure 2-8 Side view of interferometer optics and beam path .............................2-11
Figure 2-9 The Superspring. ...................................................................................... 2-13
Figure 2-10 The Superspring sphere detection system..........................................2-14
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