Superconducting Technology Assessment - nitrd

More documents

Recommendations

Info

The Northrop Grumman Space <strong>Technology</strong> (NGST) single-stage High Efficiency Cryocooler (HEC) program, quite possibly the most successful to date, was a joint effort funded by MDA, NASA, and the U.S. Air Force (Figure 8). A 35/85 K NGST High-Efficiency Pulse Tube Cryocooler is intended to simultaneously cool both focal planes and optics, removing 2 watts at 35 K and 16 watts at 85 K with a single cooler. A parallel program with Raytheon has similar objectives but uses a hybrid Stirling upper stage and pulse-tube lower stage for lower mass and improved efficiency. Large Cooling Units There are two European manufacturers of large machines: Linde in Germany and Air Liquid in France. There are a few Japanese manufacturers, but their track record is not as good as the Europeans. Dresden University in Germany is one of the few places in the world doing research on efficient refrigeration cycles. A system capable of handling kW level of heat loads cools portions of the Tevatron accelerator at Fermilab in Illinois. Systems of such size produced a refrigeration efficiency of 0.25 (Figure 9). The conceptual design of a single large system has been initiated under the HTMT program (Figure 10). Refridgerator Efficiency (percent of carnot) 100 .1 .0001 Figure 9. Refrigerator efficiency of various cooling systems. Figure 10. Concept for a large-scale system including cryogenic cooling unit for supercomputers 7 . 7 HTMT Program Phase IIII Final Report, 2002 10 1 REFRIDGERATOR EFFICIENCY AS A FUNCTION OF REFRIDGERATION AT 4.5K Small Coolers 2004 � .001 � 1m SRAM � � 1m � HRAM/DRAM � .01 Data Vortex .1 Refridgeration at 4.5 K (kW) 77 0 k � 4 0 k 50 Computer Equivalent 4.5K Refridgeration � 1 � RSFQ PEs 0.5 10 SIDE VIEW � Fiber/Wire Interconnects � 3m � 100 237
Although cooling of the 4 K circuits by immersion in LHe may be the most straightforward approach cryogenically, doing so would produce significant technical issues on the system integration front: large diameter plumbing would be required to carry the helium gas back to be recondensed and utilizing the enthalpy of the gas in order to pre-cool the I/O lines requires a complicated heat exchanger. Most importantly, the 4 K components would need to be surrounded by a He leak-tight vessel and then a vacuum space. Either the leads would have to travel to elevated temperatures with the gas, necessitating long signal travel times, or they would travel a shortest distance path that would require cryogenic vacuum feed-throughs for each of the leads. It seems likely that this approach practical only if substantial cold memory exists in the system so that only computational results are shipped to the room temperature. Otherwise, millions of high speed I/Os are needed Cooling by conduction using plates made from high thermal conductivity materials such as copper seems a more viable alternative when SCE chips, MCMs, PCBs, and I/Os are all in the same vacuum space. These plates would either have direct thermal connections to a cold plate, cooled by the refrigerator, or have liquid helium running through a set of engineered sealed passages (e.g. micro-channels or pores of Cu foam) within the plates themselves. Such systems have recently been extensively worked to provide extreme rates of heat removal from above room temperature for power amplifiers and the same physics will apply. Whether both the liquid and gas phase of He can be present might need to be investigated. Conduction cooling places greater demands on the thermal design of the system but the technical issues are familiar. Low thermal conductance paths from the chip to the cold head are essential. The temperature difference between the component being cooled and the cold box is a key issue even when large refrigerators are used to cool superconducting electronic devices. Given the severe energy penalty for compensating for this gradient by lowering the cold-plate temperature, bit-error tests should be performed for 20 KA/cm 2 circuits as a function of bias temperature as early as possible. For 1KA/cm 2 devices there is experimental evidence that circuits designed for 4.2 K operation still function well as high as 5.5 K due to the slow dependence of critical current (I c) on temperate (ref. HYPRES). Serious consideration should be given toward reducing the refrigeration load through the use of high temperature superconducting (YBCO or MgB2) cables or optical leads in conjunction with mid temperature (e.g. 30- 40 K) intercepts. More details are provided in the “Cables” section. Vibration can be a serious problem for superconducting electronics if the total magnetic field at the circuits is not uniform and reproducible. Good cryo-packaging practice requires both careful attention to magnetic shielding, minimization of vibration and relative motion of circuit components. If it proves essential, the sensitive electronic components can be mounted using a stiff (high resonant frequency) cold mass support system that has a low heat leak and is cooled via a flexible cooling strap attached to the cold plate. Keeping the strap short length minimizes the temperature drop and also reduces the vibration isolation achieved. The cryocooler itself can be mounted with flex mounts on the cryostat vacuum vessel, which has more mass than the cooled device. The reliability issues can be mitigated by using smaller cryocooler units around a central large scale cryogenic cooling unit. This approach adds modularity to the system and allows for local repair and maintenance while keeping the system running. However, the design issues resulting from the management of many cryocoolers working together are yet not well explored. 238
Page 1 and 2:
SUPERCONDUCTING TECHNOLOGY ASSESSME
Page 3 and 4:
Summary of Findings The STA conclud
Page 5 and 6:
CHAPTER 02: ARCHITECTURAL CONSIDERA
Page 7 and 8:
CHAPTER 06: SYSTEM INTEGRATION 6.1
Page 9 and 10:
INDEX OF FIGURES CHAPTER 01: INTROD
Page 11 and 12:
APPENDIX G: ISSUES AFFECTING RSFQ C
Page 13 and 14:
CONTENTS OF CD EXECUTIVE SUMMARY CH
Page 15 and 16:
LIMITATIONS OF CURRENT TECHNOLOGY C
Page 17 and 18:
State of the Industry Today, expert
Page 19 and 20:
01 This document presents the resul
Page 21 and 22:
1.2 LIMITATIONS OF CONVENTIONAL TEC
Page 23 and 24:
1.3.2 RSFQ ATTRIBUTES Important att
Page 25 and 26:
The end point of this roadmap defin
Page 27 and 28:
Structurally, a high-end computer w
Page 29 and 30:
16 ■ Chalmers University in Swede
Page 31 and 32:
Random Access Memory Options Random
Page 33 and 34:
Compact Package Feasible Thousands
Page 35 and 36:
MCMs The design of MCMs for SCE chi
Page 37 and 38:
02 No radical execution paradigm sh
Page 39 and 40:
The key challenges at the processor
Page 41 and 42:
2.2 MICROPROCESSORS - CURRENT STATU
Page 43 and 44:
2.2.3 CORE1 BIT-SERIAL MICROPROCESS
Page 45 and 46:
Potential Problems The initial vers
Page 47 and 48:
The microarchitecture of supercondu
Page 49 and 50:
2.5 MICROPROCESSORS - CONCLUSIONS A
Page 51:
2.7 MICROPROCESSORS - FUNDING In th
Page 54 and 55:
SUPERCONDUCTIVE RSFQ PROCESSOR AND
Page 56 and 57:
3.1 RSFQ PROCESSORS The panel devel
Page 58 and 59:
Circuits/ Organizations Flux-1/ NG,
Page 60 and 61:
3.1.2 RSFQ PROCESSORS - READINESS F
Page 62 and 63:
3.1.3 RSFQ PROCESSORS - ROADMAP The
Page 64 and 65:
3.1.5 RSFQ PROCESSORS - ISSUES AND
Page 66 and 67:
Since these memory concepts are so
Page 68 and 69:
Simulations show that the input int
Page 70 and 71:
SFQ RAM Status The results of five
Page 72 and 73:
Investment for SFQ Memory The inves
Page 74 and 75:
4MB MRAM BIT CELL: 1 MTJ & 1 TRANSL
Page 76 and 77:
The roadmap identifies early analyt
Page 78 and 79:
MRAM Major Issues and Concerns Mate
Page 80 and 81:
3.3 CAD TOOLS AND DESIGN METHODOLOG
Page 82 and 83:
Issues and Concerns Present simulat
Page 84 and 85:
Investment The investment estimated
Page 87 and 88:
04 By 2010 production capability fo
Page 89 and 90:
Table 4-1 summarizes the roadmap fo
Page 91 and 92:
4.1 SCE IC CHIP MANUFACTURING - SCO
Page 93 and 94:
Significant activity in the area of
Page 95 and 96:
4.3 SCE CHIP FABRICATION FOR HEC -
Page 97 and 98:
The superconductive IC chip fabrica
Page 99 and 100:
Table 4-6 shows how gate speed depe
Page 101 and 102:
Parameter spreads in superconductiv
Page 103 and 104:
4.6 ROADMAP AND FACILITIES STRATEGY
Page 105 and 106:
Figure 4-6. Timeline for developmen
Page 107 and 108:
A potential savings of ~40% in the
Page 109 and 110:
05 Packaging and chip-to-chip inter
Page 111 and 112:
98 Data Communication Requirement R
Page 113 and 114:
For further discussions of the opti
Page 115 and 116:
5.1.3 OPTICAL INTERCONNECT TECHNOLO
Page 117 and 118:
In this case, an optical receiver w
Page 119 and 120:
Examples of what has been achieved
Page 121 and 122:
5.3.4 OUTPUT: 4 K RSFQ TO ROOM TEMP
Page 123 and 124:
Figure 5-4. Superconducting 16x16 c
Page 125 and 126:
06 The design of secondary packagin
Page 127 and 128:
For this study, the readiness of th
Page 129 and 130:
6.1.3 MULTI-CHIP MODULES AND BOARDS
Page 131 and 132:
6.2. 3-D PACKAGING Conventional ele
Page 133 and 134:
6.2.3. 3-D PACKAGING - ISSUES AND C
Page 135 and 136:
Several companies have demonstrated
Page 137 and 138:
In selecting the cooling approach f
Page 139 and 140:
Another issue is the cost of the re
Page 141 and 142:
Some of the thermal and electrical
Page 143 and 144:
Optical interconnects may require t
Page 145 and 146:
6.6.4 SYSTEM INTEGRITY AND TESTING
Page 147 and 148:
Appendix A
Page 149 and 150:
■ Construct a detailed supercondu
Page 151 and 152:
Appendix B
Page 153 and 154:
140 George Cotter Nancy Welker Doc
Page 155 and 156:
Appendix C
Page 157 and 158:
144 TERMS/DEFINITIONS IHEC Integrat
Page 159 and 160:
Appendix D
Page 161 and 162:
The time-dependent behavior of this
Page 163 and 164:
RSFQ electronics is faster and diss
Page 165 and 166:
Similar to CMOS, the irreducible po
Page 167 and 168:
Appendix E
Page 169 and 170:
The report further identified four
Page 171 and 172:
Analog high temperature superconduc
Page 173 and 174:
Appendix F
Page 175 and 176:
Only one significant effort to arch
Page 177 and 178:
Execution Models Organizing hardwar
Page 179 and 180:
Development Issues and Approaches T
Page 181 and 182:
Appendix G
Page 183 and 184:
The two-junction comparator, the ba
Page 185 and 186:
Bias Currents A major cause of degr
Page 187 and 188:
Power and bias current Power is dis
Page 189 and 190:
Appendix H
Page 191 and 192:
SMT MRAM Another direct selection s
Page 193 and 194:
Speed and Density The first planned
Page 195 and 196:
0.08 0.06 0.04 0.02 30 40 50 60 70
Page 197 and 198:
Appendix I
Page 199 and 200: Table 1 Representative Nb and NbN-B
Page 201 and 202: ground plane may be located either
Page 203 and 204: Fig. 4. Junction fabrication proces
Page 205 and 206: Table 6 Junction Array Summary of T
Page 207 and 208: Fig. 11. Ground plane planarization
Page 209 and 210: B. Yield Yield measurements are an
Page 211 and 212: Fig. 17. Photograph of the FLUX-1r1
Page 213 and 214: [47] B. Bumble, H. G. LeDuc, J. A.
Page 215 and 216: Appendix J
Page 217 and 218: Fig. 2. The Schematic View describe
Page 219 and 220: Fig. 4. The VHDL View captures the
Page 221 and 222: Fig. 6. LMeter is specialized softw
Page 223 and 224: Fig. 8. Layout-versus-Schematic ver
Page 225 and 226: Appendix K
Page 227 and 228: 1. CURRENT STATUS OF OPTICAL INTERC
Page 229 and 230: 1.2. CURRENT OPTICAL INTERCONNECT R
Page 231 and 232: If technology, power, or cost limit
Page 233 and 234: 3.4 COARSE VS. DENSE WAVE DIVISION
Page 235 and 236: 3.5 DEVELOPMENTS FOR LOW TEMPERATUR
Page 237 and 238: 5. ROADMAP The roadmap below shows
Page 239 and 240: Appendix L
Page 241 and 242: The bandwidth, chip density and int
Page 243 and 244: While using short flex cables is th
Page 245 and 246: We must note that the reparability
Page 247 and 248: Figure 7. A typical cryocooler encl
Page 249: Small Cryocoolers Among commercial
Page 253 and 254: Supplying DC current to all of the
Page 255 and 256: These properties enable the possibi
Page 257: For additional copies, please conta
show all

Superconducting Technology Assessment - nitrd

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?