Reliability in Scientific Research (Improving the Dependability of Measurements, Calculations, Equipment, and Software)

"Covering many techniques widely used in research, this book will help researchers in the physical sciences and engineering solve troublesome, and potentially very time consuming, problems in their work. The book deals with technical difficulties that often arise unexpectedly during the use of various common experimental methods, as well as with human error. It provides preventive measures and solutions for such problems, thereby saving valuable time for researchers. Some of the topics covered are: sudden leaks in vacuum systems, electromagnetic interference in electronic instruments, vibrations in sensitive equipment, and bugs in computer software. The book also discusses mistakes in mathematical calculations, and pitfalls in designing and carrying out experiments. Each chapter contains a summary of its key points, to give a quick overview of important potential problems and their solutions in a given area"-- Provided by publisher Cover......Page 1 Half-title......Page 3 Title......Page 5 Copyright......Page 6 Dedication......Page 7 Contents......Page 9 Preface......Page 21 Abbreviations......Page 23 1.2 Central points......Page 25 1.3.1.2 Finding out what is known......Page 29 1.3.1.3 A digression on sources of information......Page 30 1.3.1.5 Paying attention to detail......Page 31 1.3.2.1 Frequency of problems caused by human error......Page 32 1.3.2.2 Dominant types of human error – related problems......Page 33 1.3.2.3 Dominant causes of human error – related problems......Page 34 Frustration......Page 35 1.3.3.2 Preparation and planning......Page 36 1.3.3.3 Automation......Page 37 1.3.3.6 Omissions caused by strong habits......Page 38 Lighting......Page 39 Air conditioning......Page 40 1.3.3.8 Design of systems and tasks......Page 41 1.3.3.9 Procedures and documentation......Page 42 1.3.3.10 Labeling......Page 43 1.3.4.1 Communication......Page 44 1.3.4.3 The value of division of labor......Page 45 1.3.4.5 Problems with communal equipment......Page 46 1.3.4.7 Presence of non research-related people in the laboratory......Page 47 1.4.1 Record-keeping......Page 48 1.4.3 Troubleshooting equipment and software......Page 49 1.5 Reliability of information......Page 52 1.3.2 Some data on human error......Page 55 1.3.4 Interpersonal and organizational issues......Page 56 1.4.3 Troubleshooting equipment and software......Page 57 References......Page 58 2.2.3 Errors in technique......Page 60 2.2.5 Errors in published tables......Page 62 2.2.6 Problems arising from the use of computer algebra systems......Page 63 2.2.7 Errors in numerical calculations......Page 64 2.3.2 Use of diagrams......Page 66 2.3.4 Keeping things simple......Page 67 2.3.7 Outsourcing the problem......Page 68 2.3.10 Practices for manual calculations......Page 69 2.4.1 General remarks......Page 70 2.4.3 Predicting simple features of the solution from those of the problem......Page 71 2.4.5 Further checks involving internal consistency......Page 72 2.4.8 Check calculations......Page 73 2.4.9 Comparing the results of the calculation against known results......Page 75 2.4.10 Detecting errors in computer algebra calculations......Page 76 2.3 Strategies for avoiding errors......Page 77 2.4 Testing for errors......Page 78 References......Page 79 3.2 Stress derating......Page 82 3.3.2 Some causes and characteristics......Page 84 3.3.3 Preventing and solving intermittent problems......Page 86 3.4.1.2 Reduction and regulation of room temperatures......Page 87 3.4.1.3 Measures for preventing the overheating of equipment......Page 88 3.4.2.1 Definitions......Page 89 3.4.2.2 Harmful effects of moisture......Page 90 3.4.2.4 Avoiding moisture problems......Page 91 3.5.1 Introduction......Page 92 3.5.2 Large-amplitude vibration issues......Page 93 3.5.3.1 Measurement difficulties and sources of vibration......Page 95 Selecting a suitable site......Page 97 Isolating sensitive apparatus from floor vibrations......Page 100 Isolating vibrations in pumping lines, electrical cables, and pipes......Page 102 Controlling vibrations at their source......Page 104 Rigidity and stability of optical mounts......Page 105 Other measures......Page 106 Brownouts and sags......Page 107 Swells and transients......Page 108 3.6.2 Investigating power disturbances......Page 109 3.6.3.2 Reduction of RF electrical noise......Page 110 3.6.3.4 Uninterruptible power supplies......Page 111 Double-conversion types......Page 112 Selection and use of UPSs......Page 113 3.6.3.5 Standby generators......Page 114 3.7.2 Conditions encountered during transport......Page 115 3.7.3 Packaging for transport......Page 117 3.7.5 Insurance......Page 119 3.8.2 Oil and water in compressed air supplies......Page 120 3.8.3 Silicones......Page 121 3.9 Galvanic and electrolytic corrosion......Page 123 3.10 Enhanced forms of materials degradation related to corrosion......Page 124 3.11.2 Prevalence and examples of fatigue......Page 125 3.11.3 Characteristics and causes......Page 126 3.12 Damage caused by ultrasound......Page 128 3.2 Stress derating......Page 129 3.4.2 Moisture......Page 130 3.5.3 Interference with measurements......Page 131 3.6 Electricity supply problems......Page 132 3.7 Damage and deterioration caused by transport......Page 133 3.9 Galvanic and electrolytic corrosion......Page 134 References......Page 135 4.2 Using established technology and designs......Page 140 4.4 Understanding the basics of a technology......Page 141 4.5 Price and quality......Page 142 4.6.2 Place of origin of a product......Page 143 4.6.6 True meaning of specifications......Page 144 4.6.8 Testing items prior to purchase......Page 145 4.7.3 Reliability incentive contracts......Page 146 4.7.4 Actions to take before delivery......Page 147 4.8 Use of manuals and technical support......Page 148 Summary of some important points......Page 149 References......Page 150 5.2 Commercial vs. self-made items......Page 151 5.3 Time issues......Page 152 5.5 Making apparatus fail-safe......Page 153 5.6 The use of modularity in apparatus design......Page 154 5.7 Virtual instruments......Page 155 5.8 Planning ahead......Page 156 5.9 Running the apparatus on paper before beginning construction......Page 157 5.11 Designing apparatus for diagnosis and maintainability......Page 158 5.14 Ergonomics and aesthetics......Page 159 Summary of some important points......Page 160 References......Page 161 6.1 Introduction......Page 162 6.2 Classifications of leak-related phenomena......Page 163 6.3 Common locations and circumstances of leaks......Page 164 6.4 Importance of modular construction......Page 165 6.5.1 General points......Page 166 6.5.2 Leak testing raw materials......Page 167 6.5.3 Stainless steel......Page 168 6.5.7 Copper......Page 170 6.6.1 Cleaning agents......Page 171 6.6.2 Vacuum-pump fluids and substances......Page 172 6.6.4 Other type of contamination......Page 173 6.7.1 Worker qualifications and vacuum-joint leak requirements......Page 174 6.7.2.2 Semi-permanent joints......Page 175 6.7.2.4 Improving bonding characteristics with surface coatings......Page 176 6.7.2.7 Joining of bellows......Page 177 6.7.4.1 Arc welding......Page 178 6.7.4.2 Welding of specific materials......Page 179 6.7.4.3 Electron-beam welding......Page 180 6.7.5 Brazing......Page 181 6.7.6.1 Introduction......Page 182 Purity requirements......Page 183 Solder joints in low-temperature applications......Page 184 6.7.6.5 Design of the solder joint, and the soldering process......Page 186 6.7.6.6 Soldering difficult materials......Page 187 6.8 Use of guard vacuums to avoid chronic leak problems......Page 188 6.9.1 Items involving fragile materials subject to thermal and mechanical stresses......Page 189 6.9.2 Water-cooled components......Page 190 6.9.3 Metal bellows......Page 191 6.10.1.1 Introduction......Page 194 Introduction......Page 196 Helium leak-testing techniques......Page 197 6.10.1.3 Some potential problems during leak detection......Page 198 Introduction......Page 199 General methods......Page 200 Superleaks......Page 201 Locating large leaks at very large distances......Page 202 6.11 Leak repairs......Page 203 6.5 Selection of materials for use in vacuum......Page 205 6.6 Some insidious sources of contamination and outgassing......Page 206 6.7.4 Welding......Page 207 6.7.6 Soldering......Page 208 6.9 Some particularly trouble-prone components......Page 209 6.11 Leak repairs......Page 210 References......Page 211 7.2.1.1 General issues concerning mechanical primary pumps......Page 214 Prevention of contamination from pump oil......Page 215 Leaks......Page 217 7.2.1.3 Oil-free scroll and diaphragm pumps, and other “dry” positive-displacement primary pumps......Page 218 Introduction......Page 219 Vacuum-system contamination......Page 220 Automatic protection devices......Page 221 Introduction......Page 222 Magnetic-bearing turbopumps......Page 223 Consequences of improper venting......Page 224 7.2.2.3 Cryopumps......Page 225 Advantages......Page 226 Limitations......Page 227 Deterioration and failure modes......Page 228 Sublimation pumps......Page 229 Non-evaporable getter pumps......Page 230 7.3.1 General points......Page 231 7.3.3 Capacitance manometers......Page 232 7.3.5 Bayard–Alpert ionization gauges......Page 233 7.4.1 Human error and manual valve operations......Page 234 7.4.2 Selection of bakeout temperatures for UHV systems......Page 235 7.4.3 Cooling of electronics in a vacuum......Page 236 7.2.1 Primary pumps......Page 237 7.2.2 High-vacuum pumps......Page 238 7.4 Other issues......Page 239 References......Page 240 8.2.1 Overview of conditions that reduce reliability......Page 242 Advantages and disadvantages......Page 243 Methods for operating flexural mechanisms......Page 245 8.2.2.2 Direct versus indirect drive mechanisms......Page 246 8.2.3 Precision positioning devices in optical systems......Page 247 8.2.5.1 Plain bearings......Page 248 8.2.5.2 Rolling-element bearings......Page 249 8.2.7.1 Introduction......Page 251 8.2.7.2 Selection of materials for sliding contact......Page 252 8.2.7.4 Liquid lubricants for harsh conditions......Page 253 8.2.7.5 Dry lubricants......Page 255 Damage to sealing surfaces and seals......Page 257 Leaks due to contaminants on seals and sealing surfaces......Page 258 Tightening of threaded fasteners on flanges......Page 259 Introduction......Page 260 Materials properties and selection......Page 261 Installation and removal......Page 262 8.2.8.3 Flat metal gasket seals of the “ConFlat®” or “CF” design......Page 263 8.2.8.4 Metal-gasket face-sealed fittings for small-diameter tubing......Page 264 8.2.8.5 Helicoflex® metal O-ring seals......Page 265 8.2.8.6 Indium seals for cryogenic applications......Page 266 8.2.8.8 Weld lip connections......Page 269 8.2.9.1 Devices employing sliding seals......Page 270 8.2.9.3 Magnetic fluid seals......Page 271 8.2.9.4 Magnetic drives......Page 272 8.2.9.5 Use of electric motors in the sealed environment......Page 273 8.2.10.1 Introduction......Page 274 Pressure relief valves......Page 276 Rupture discs......Page 278 8.2.10.4 Metering valves......Page 279 8.2.10.6 Gate, poppet, and load lock vacuum valves......Page 281 8.2.10.7 Solenoid- and pneumatic-valves......Page 282 8.2.10.8 Advantages of ball valves – particularly for water......Page 283 8.3.2 Selection of materials......Page 284 8.3.3 Construction issues......Page 285 8.3.5 Filter issues......Page 286 8.4.1 Introduction......Page 287 8.4.2.1 Introduction......Page 289 8.4.2.3 Termination of hoses......Page 290 8.4.2.4 Automatic detection of water leaks......Page 291 8.4.3.2 Removal and control of impurities......Page 292 8.4.5 Condensation......Page 294 Further reading......Page 295 8.2.3 Precision positioning devices in optical systems......Page 296 8.2.7 Lubrication and wear under extreme conditions......Page 297 8.2.8.2 O-rings......Page 298 8.2.8.7 Conical taper joints for cryogenic applications......Page 299 8.2.10.1 Introduction......Page 300 8.2.10.6 Gate, poppet, and load-lock vacuum valves......Page 301 8.3 Systems for handling liquids and gases......Page 302 8.4.3 Water purity requirements......Page 303 References......Page 304 9.1 Introduction......Page 309 9.2 Difficulties caused by the delicate nature of cryogenic apparatus......Page 310 9.3 Difficulties caused by moisture......Page 312 9.4 Liquid-helium transfer problems......Page 313 9.5 Large pressure buildups within sealed spaces......Page 314 9.6 Blockages of cryogenic liquid and gas lines......Page 315 9.8 Cryogen-free low-temperature systems......Page 317 9.9 Heat leaks......Page 318 9.10.3.1 Thermal conductance vs. contact force......Page 320 9.10.3.3 Indium foil as a gap filler......Page 321 9.10.3.4 Optimizing heat transport through direct metal-to-metal contacts......Page 322 9.11 1 K pots......Page 324 9.12.3 Measurement errors due to RF heating and interference......Page 325 9.12.4 Causes of thermometer calibration shifts......Page 326 9.13 Problems arising from the use of superconducting magnets......Page 327 9.3 Difficulties caused by moisture......Page 329 9.7 Other problems caused by the presence of air in cryostats......Page 330 9.12 Thermometry......Page 331 References......Page 332 10.2 Temperature variations in the optical path......Page 334 10.3 Temperature changes in optical elements and support structures......Page 336 10.4 Materials stability......Page 338 10.5 Etalon fringes......Page 339 10.6.1 Introduction......Page 342 10.6.2.1 High-power light systems......Page 345 10.6.2.3 Diffraction gratings......Page 346 10.6.3 Measures for protecting optics......Page 347 10.6.4 Inspection......Page 350 10.6.5.1 Introduction......Page 351 10.6.5.2 Some general cleaning procedures......Page 352 10.6.5.3 Some cleaning agents to be avoided in the cleaning of optics......Page 354 10.6.5.5 Vapor degreasing......Page 355 10.6.5.8 Cleaning by using reactive gases......Page 356 10.7.1 Problems with IR and UV materials caused by moisture, and thermal and mechanical shocks......Page 357 10.7.3 Corrosion and mold growth on optical surfaces......Page 358 10.7.4.2 Sapphire......Page 359 10.7.4.5 Fused silica or silicon carbide diffraction gratings......Page 360 10.8.3 Insensitivity to crosstalk and EMI, and sensitivity to environmental disturbances......Page 361 10.9.1.1 Introduction......Page 362 10.9.1.4 Microphonics......Page 363 10.9.1.5 Active compensation methods for reducing noise and drift......Page 364 10.9.2.1 Diode lasers......Page 365 10.9.2.3 Other gas lasers......Page 366 10.9.3 Some incoherent light sources......Page 367 10.11 Photomultipliers and other light detectors......Page 368 10.2 Temperature variations in the optical path......Page 369 10.5 Etalon fringes......Page 370 10.6 Contamination of optical components......Page 371 10.8 Fiber optics......Page 372 10.9 Light sources......Page 373 References......Page 374 Importance of grounding arrangements......Page 377 The nature of the problem......Page 378 Unexpected behavior......Page 380 Planning ground systems and the use of ground maps......Page 381 Single-point grounding......Page 383 The provision of floating power......Page 384 Opening ground loops in the signal path......Page 386 Some methods of reducing the effects of unavoidable ground loops......Page 391 11.2.1.3 Detecting ground loops......Page 392 11.2.2.1 Introduction......Page 394 Precautionary measures......Page 396 Shields......Page 397 Filters......Page 398 Radio-frequency grounding......Page 400 Shielded rooms......Page 401 11.2.2.4 Detecting and locating RF noise in the environment......Page 402 11.2.3.1 Affected items......Page 403 11.2.3.3 Prevention of interference......Page 404 11.2.4 Some EMI issues involving cables, including crosstalk between cables......Page 405 11.3.1 The phenomena and their effects......Page 406 11.3.2 Conditions likely to result in discharges......Page 407 11.3.3 Measures for preventing discharges......Page 408 11.3.4 Detection of corona and tracking......Page 410 11.4.1 The difficulties......Page 411 11.4.2 Some solutions......Page 412 11.5.1 Origins, character, and effects of ESD......Page 414 11.5.2 Preventing ESD problems......Page 417 11.6 Protecting electronics from excessive voltages......Page 418 11.7 Power electronics......Page 419 11.8.1.2 Switch selection for low and high current and voltage levels......Page 421 11.8.1.3 Switching large inductive loads......Page 422 11.8.1.5 Alternatives to mechanical switches, relays and thermostats for improved reliability......Page 423 11.8.3 Fans......Page 424 11.8.5 Batteries......Page 425 Further reading......Page 427 11.2.1 Grounding and ground loops......Page 428 11.2.2 Radio-frequency interference......Page 429 11.4 High-impedance systems......Page 430 11.6 Protecting electronics from excessive voltages......Page 431 11.8.4 Aluminum electrolytic capacitors......Page 432 References......Page 433 12.1 Introduction......Page 437 12.2.1.1 Modes of failure......Page 438 Weakness of solder and the need for mechanical support......Page 439 Selection of solder......Page 440 12.2.1.4 Electrostatic discharge (ESD) issues......Page 442 Dissolution of thin conductors (especially gold) by solder......Page 443 Gold embrittlement......Page 444 Use of solder in high-temperature environments or high-current circuits......Page 445 12.2.2.1 Crimp connections......Page 446 12.2.2.2 Welding and brazing......Page 447 12.2.2.3 Use of mechanical fasteners in high-current connections......Page 448 12.2.3.1 Ultrasonic soldering......Page 449 12.2.3.2 Friction-soldering methods......Page 450 12.2.3.3 Solders for joining difficult materials......Page 451 12.2.3.8 Silver epoxy......Page 452 12.2.4 Ground contacts......Page 453 12.2.5 Minimization of thermoelectric EMFs in low-level d.c. circuits......Page 454 12.3.2 Failure modes......Page 455 12.3.3.1 Human error......Page 457 12.3.3.2 Damage and degradation during normal operation and use......Page 458 12.3.3.3 Corrosion......Page 459 12.3.4.1 General points......Page 461 12.3.4.2 Contact materials......Page 466 12.3.4.3 Connector derating in the presence of large currents or voltages......Page 467 12.3.4.5 Provision of a ground pin in multi-pin connectors......Page 468 12.3.5.2 High-voltage connectors......Page 469 12.3.5.3 High-current connectors......Page 470 12.3.5.4 Mains-power plugs and receptacles......Page 471 12.3.6.2 Reducing contact wear and corrosion......Page 472 12.3.6.3 Minimizing crosstalk problems in multi-pin connectors......Page 473 12.3.6.5 Inspection and cleaning......Page 474 12.4.1 Modes of failure......Page 475 12.4.2.1 Vulnerable cable types......Page 476 12.4.2.3 Cable deterioration and ageing......Page 477 12.4.3.1 Provenance......Page 478 12.4.3.3 Choosing cables for use under conditions of flexure and vibration......Page 479 12.4.4.1 Grounding of cable shields......Page 480 12.4.4.2 Choice of cable-shield coverage......Page 481 12.4.4.4 Attachment of shielded cables to their connectors (“pigtail” problems)......Page 483 12.4.4.5 Rapid fixes for cables with inadequate shields......Page 484 12.4.4.6 Use of twisted-wire pairs in the presence of low-frequency interfering fields......Page 485 12.4.5.1 GP-IB cable assemblies......Page 486 12.4.6.1 Installation......Page 487 12.4.6.4 Cable inspection and replacement......Page 489 Selection and removal of enamel19......Page 490 Wiring for cryogenic systems......Page 492 Soldering small enameled wires......Page 494 12.5.2.1 Resistance......Page 495 12.5.3 High-resistance and open- and short-circuit intermittent faults......Page 496 12.5.4 Use of infrared thermometers on high-current contacts......Page 497 12.5.6 Fault detection and location in cables......Page 498 12.2.1 Soldering......Page 499 12.2.4 Ground contacts......Page 500 12.3.3 Causes of connector failure......Page 501 12.3.5 Some particularly troublesome connector types......Page 502 12.4.2 Cable damage and degradation......Page 503 12.4.5 Some comments concerning GP-IB and ribbon cables......Page 504 12.4.7 Wire issues – including cryostat wiring......Page 505 References......Page 506 13.2.1 Selection......Page 511 13.2.2 Some common causes of system crashes and other problems......Page 513 13.3 Industrial PCs and programmable logic controllers......Page 514 13.4.1.1 Risks and causes of hard-drive failure......Page 515 13.4.1.2 Use of redundant disc (RAID) systems......Page 516 13.4.1.4 Recovery of data from failed hard drives......Page 517 13.4.2 Power supplies......Page 518 13.4.3 Mains-power quality and the use of power-conditioning devices......Page 519 13.4.5.2 Data errors on RS-232 links......Page 520 13.4.5.4 Advantages of GP-IB and USB......Page 521 13.4.5.7 References on RS-232, RS-485, and GP-IB......Page 522 13.5.2 Some backup techniques and strategies......Page 523 13.6 Long-term storage of information and the stability of recording media......Page 524 13.7.2 Viruses and their effects......Page 526 13.7.4 Measures for preventing virus attacks......Page 527 13.8.1 Avoiding early releases and beta software......Page 528 13.8.2 Questions for software suppliers......Page 529 13.8.4 Open-source software......Page 530 13.10.2 Graphical languages......Page 531 13.10.3 Some concerns with graphical programming......Page 532 13.11 Precautions for collecting experimental data over extended periods......Page 533 13.12.1 Introduction......Page 534 13.12.2.2 Code requirements......Page 535 Architecture......Page 536 Properties of routines......Page 537 13.12.3.1 Use of pseudocode for detailed design......Page 538 13.12.3.2 Pair programming......Page 540 General points......Page 541 13.12.3.5 Structured programming......Page 542 13.12.3.6 Naming of variables and routines......Page 543 13.12.3.8 Code documentation......Page 544 13.12.3.9 Testing program inputs for errors......Page 545 13.12.3.10 Common programming errors......Page 546 13.12.4.1 Introduction......Page 547 General approach......Page 548 Debugging tools......Page 549 13.13 Using old laboratory software......Page 550 13.2.1 Selection......Page 551 13.4.1 Hard-disc drives......Page 552 13.5 Backing-up information......Page 553 13.8 Reliability of commercial and open-source software......Page 554 13.12.1 Introduction......Page 555 13.12.3 Detailed program design and construction......Page 556 References......Page 557 14.2 Knowing apparatus and software......Page 560 14.3 Calibration and validation of apparatus......Page 561 14.4 Control experiments......Page 562 14.6.1 Introduction......Page 564 14.6.3 Subconscious biases in data analysis......Page 565 14.6.4 Subconscious biases caused by social interactions......Page 566 14.8.1 Introduction......Page 567 14.8.2 The case of polywater......Page 568 14.8.3 Some useful measures......Page 570 14.9.1 Introduction......Page 571 14.9.3 Laboratory visits as a way of acquiring missing expertise......Page 572 14.9.4 A historical example: measuring the Q of sapphire......Page 573 14.10 Low signal-to-noise ratios and statistical signal processing......Page 575 14.11.2 A brief outline and history......Page 576 14.11.3 Origins of the problems......Page 577 14.11.4 Conclusions......Page 581 14.12 Understanding one’s apparatus and bringing it under control: the example of the discovery of superfluidity in He3......Page 582 Further reading......Page 583 14.5 Failure of auxiliary hypotheses as a cause of failure of experiments......Page 584 14.9 Reproducibility of experimental measurements and techniques......Page 585 References......Page 586 Index......Page 588