The Development of an ExperimentalElectron-Beam-Addressed Memory Module

John KellyStanford Research Institute

Introduction

The various technologies needed to build a successfulelectron-beam-addressed memory (EBAM) have beenevolving for over a decade, and are now sufficientlyestablished to build a viable, economical system. Recentwork at SRI indicates that EBAM will be an importantcontender for low-cost, large memory systems withimproved random-access capability, high reliability, andhigh data rates. This will be achieved in small volume andwithout the use of moving parts. The potential applicationsof such a mass memory system are widespread, rangingfrom direct drum and disk replacement to new systemswith architectures that would take advantage of improvedrandom access times and increased data rates.

The major attraction of the EBAM concept lies in theability to produce relatively large capacity, fast access units

32

at low cost. For example, to build a memory of 109 to101 0 bits, it is desirable to have a module of the order of106 to 107 bits, since otherwise the problems ofinterconnection and packaging become formidable. Neitheris it desirable to have each module made up of too manysmaller units, again a source of unreliability and expense.

In the case of the EBAM, the tube is the module, whichin first production systems is likely to be of the order of4 X 106 bits with an access time of several microsecondsand a system cost of 0.02 cents per bit. Furtherdevelopments will undoubtedly lead to even greatercapacities and sub-microsecond access times.

It is therefore considered that the EBAM is notcompeting head-on with semiconductor devices, includingcharge coupled devices, or magnetic devices such asmagnetic bubbles, drums, and disks. None of these combineall the desired qualities-high bit capacity, fast access time,

COMPUTER

fIll

ELECTRON GUN

I -L ll ii DEFLE~ AD

- STORAGEI

PLANESYEDEFLECMOR RSEADOUT P- LENS SYSTEM

SA-1 7-78-3RFigure 1. Major Components of EBAM Tube

low cost per bit, wide versatility of data format, low powerconsumption, small volume, and simplicity of inter-connects-that are uniquely achieved in the EBAM.However, any particular specification may be equaled orexceeded by one or the other of these technologies. Forexample, semiconductor memories are relatively low costand low volume, and can have high speed and low powerconsumption. Attempts are being made to increase thecapacity. This implies making the current chip sizes largerthan at present, or putting more circuitry on the existingarea. Eight-kilobit devices are available and larger capacitieswill appear with time. However, as circuit complexityincreases, there will be tremendous problems in achievingsufficiently high yields to keep the costs down. Even withthe acceptance of electron beam lithography and refinedprocessing techniques, there are tremendous barriers to besurmounted.

The principal components and operation of an EBAMtube are illustrated in Figure 1. The components are similarto those found in a cathode ray tube. A beam of electronsis generated by an electron gun and focused by means of allelectron lens onto the storage target where the beam cancause some local physical change. The bit size correspondsapproximately to that of the size of the electron beam atthe storage target. Addressing is achieved by deflecting thebeam to different locatiops in the target plane. In theillustration, both the lens and the deflector areelectrostatic. Either random access or block access can beachieved, depending on the manner in which the target isscanned. Thus the beam can be used to interrogateindividual locations on the target surface (bit access), or itcan be scanned across the surface in a TV-like scan to readblocks of data (block access).

In the SRI system, information is stored by a chargedeposited by the electron beam on the surface of anelectrostatic storage target. In readout, the presence of astored charge-or lack of it-is detected by analysis of thevelocities of the secondary electrons created by the primarybeam as they return from the target surface. The energyanalyzer permits electrons from ONE-state bits to pass,thereby producing a current pulse at the tube output. Toillustrate the general capability of the EBAM concept, aspecification for an early production system based on theuse of 16 tubes in parallel is given below (see Table I). Thissystem specification is given as an example of the memorycapability that can be produced without significant furtherresearch. Naturally higher capacities can be achieved byusing larger numbers of tubes in different configurations.The cost of these first systems is estimated to be 0.024 perbit for a commercial system. Figure 2 shows the general

February 1975

System capacity:

Configuration:

Parity:

Access time:

Writing speed:

Reading speed:

Readout:

Refresh:

Power off volatility:

Power consumption:

Volume:

Weight:

Tube life:

6.4 X 107 bits

16 tubes of 4 X 106 bits operatingin parallel. Block oriented, 1000X 16 bit words or less.

As required

3 /is to any block

1 Mbit (per channel)16 Mbits (per system)10 Mbit (per channel)160 Mbits (per system)

Nondestructive*

Periodic (every 1 minute)8 hours (no flood beam)Indefinite (with flood beam)500 W (7.8 ,1W per bit)

3 ft3

< 100 lb

>2 years

*Information is only partially degraded by the reading process, andfull storage level can be restored by refresh.

D

i

C.)

0

Ul

10-4 10-2ACCESS TIME - seconds

TA-720522-1 1 5R

Figure 2. Capacity and Access Time Comparison with Other I

Memory Technologies

33

Table 1. Sample EBAM System Specification

performance of an EBAM memory compared with othermemory technologies. In this figure, memory capacity isplotted against access time. In general, this particular typeof graph can be misleading; since it is not possible tocompare all the types of memory on a bit-by-bit ormodule-by-module basis without producing a very largenumber of charts. In this chart each zone indicates the fullrange of chips and modules. The chart illustrates well thatthe EBAM technology offers memories of disk or drum-likecapacities with essentially the access time of mainframememory. EBAM systems are not yet available as productionitems. However, rapid progress is being made at GE, atMicro-Bit, and at SRI. In early 1974, SRI delivered anexperimental EBAM module to the USAF AvionicsLaboratory at Wright-Patterson AFB.' 2 Although havingsomewhat limited specifications, this equipment constitutesa milestone in EBAM system development.

Technology

.Electronics An EBAM relies heavily on the availability ofhighly stable electronic components. Such componentshave only recently become available. For example, it is nowpossible to buy the required high-voltage power supplieswith stabilities of better than one part in 104 for less than$150 (OEM). It is also possible to obtain sufficientlyprecise digital-to-analog converters with fast settling times.These are the most expensive components in the system.Specifications are still being improved and costs will bereduced further.

Electron Optics Many changes have occurred inundramatic but highly significant ways. The art of gun andlens design has improved substantially with the use ofcompyters. The factors necessary to achieve reliable, stableperformance are now well understood. This knowledge hasbeen gained in the tube industry and from the developmentof instruments such as the scanning electron microscope. Inaddition, there have been major improvements in deflectordesign. For example, an electrostatic octupole deflector wasdeveloped by the author under a program sponsored by theU.S. Army in 1969.3 This deflector enables significantlylower aberrations to be obtained across the deflection field.At the same time good sensitivity and a common center ofdeflection are achieved.

Cathode Life Dispenser cathodes with a proven life inexcess of. 10,000 hours and a potential of 50,000 hours arereadily 'ayailable. These cathodes have adequate brightnessfor the first generation of tubes. Historically, the cathodehas been the limiting factor in tube operational life. Theavailability of these cathodes has changed this situation.

Silicon Technology The availability of a wide range ofsilicon technology (especially electron lithography andsophisticated etching techniques) has greatly contributed tothis changing scene. Storage medium fabrication has shownsignificant advances.

Tube Technology Steady advances over the past severalyears in vacuum technology, in vacuum materials, and inassembly techniques ensure that an EBAM memory tubecan be made economically and still be very rugged.

34

The Storage Target

Although all of the above technologies are extremelyimportant, the selection of a suitable storage medium is themost important, since the storage target itself determinesmost of the operating parameters, including beam energy,current density, beam diameter, electronics requirements,configuration of the readout system, operating temperaturerange, error rate, and perhaps the life of the tube itself.

Many materials and operating schemes have beenproposed for EBAMs; however, all of the groups known tobe working on EBAMs appear to be using silicon-basedtargets and electrostatic charge storage of some form.4,5 Asectional drawing of the SRI target is shown in Figure 3. Itconsists of a large MOS capacitor in which a closely spacedarray of holes has been etched through the gate metal andpartway through the oxide. Metal is then deposited in thebottom of these etched holes to form at array ofmicrocapacitors that are electrically isolated both from thesilicon substrate and from the gate metal, but are moreclosely coupled capacitatively to the silicon than to thegate. These targets have been made with a range of holesizes and spacings. Quarter-inch targets with 0-M (micron)

MUCAP(MICROCAPACITOR)

STORAGE ELECTRODES

BAS

/ \ ~METAL GATE

7:2 ~~~~~~~~~S0 14 onTA-720543-1 R

Figure 3. The Mucap (Microcapacitor) Storage Medium

Figure 4. Scanning Eectron Micrograph of Storage Target (6p holes)

COMPUTER

diameter holes on 9-,u centers are in regular use. Targetshaving 0.5-M holes on i.2-, centers have been made overlimited areas in the past. A part of a regular storage target isshown in Figure 4. These targets are made using electronlithography and special etching processes developed at SRI.The result is a high degree of uniformity and a lowincidence of defects.

In some ways the ideal target would present astructureless surface to the electron beam so that anaddressed location would be determined by the impactpoint of the deflected electron beam and not by thestructure on the target. In consequence, and because it isnot possible to make a completely perfect target, thestorage medium is operated in a "quasi-continuous" mode.The microcapacitor dimensions and spacings are made smallcompared with the beam diameter, so that the illuminatingbeam covers several microcapacitors at each addresslocation, a typical number of capacitors being nine in ourpresent work. Information is stored on the microcapacitorsas a charge; 'a negative charge corresponds to a stored ONE,and a zero charge correspoilds to a ZERO. The basicreading and writing processes are best understood byreference to a single mucap element.

(42 eV)

IOV.

-40 V

e)z0G

-JwU-

0

wco

z

The reading operation is the easiest to understand and isillustrated in Figure 5. At the top is shown a ONE-statemucap. Note that the mucap is charged negatively to about-40 V and that the base is held at -50 V. Primaryelectrons striking the mucap surface generate secohdaryelectrons, which are accelerated out of the mucap cavitythrough the stored potential drop. The energy spectrum ofthese electrons is illustrated at the right. There are threeprincipal groups of electrons. First are the very slowsecondary electrons, created by the primaries striking thegate metal. Second are the accelerated secondary emissionelectrons from the mucap surface. Third are the elasticallyscattered electrons with approximately the primary beamenergy, Vp. The stored information is represented by thecentral peak. In the lower part of the figure, a ZERO isillustrated; the stored potential is approximately that of thegate metal. In reality, it is usually slightly positive withrespect to the gate. In this case, secondary electrons beingemitted from the mucap surface are not accelerated as theyleave the st6rage element and combine with the slowsecondaries from the gate metal in the energy spectrumnshown at the right. Thus the central peak referred to aboveis absent during reading of ZERO-state elements. It is

2

7/7J/,'X7JJJ777JJJJ7V$,VB (-50 V)

PASS BAND

Vi Vp

(a) READ ONE

(0 eV)

I~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

C,)z0

0

UJ-JILwLL0

w

Dz

2 V1 VpENEIRGY

SA-1 778-4R

(b) READ ZERO

Figure 5. Zero and One States and Reading Mechanisms

February 1975

ov.

2 V \

VB (-50 V)

I I--O/

35

therefore relatively simple to incorpQrate an energyanalyzer into the electron optical system in order to passonly the central band of electrons. Measurements on ourpresent analyzer indicate that a ratio of 100:1 between thetwo states is readily obtainable.

The writing process is somewhat complex, and asimplified description will be given here. In the presentmode of operation, writing entails using a primary beamenergy that creates more secondary electrons at theemitting surface than the primary electrons arriving; i.e.,the secondary electron emission coefficient is greater thanunity. Under these conditions, the mucap potential willalways tend toward the gate metal potential under electronbombardment. This will happen whether the mucap isinitially positive or negative, since when the mucap ispositive the slow secondaries created at the surface cannotescape from the mucap cavity and are returned to themucap surface, which therefore has an effective secondaryemission coefficient of less than unity.

According to the above description, reading a ONE statemucap can be expected to change the ONE to a ZERO.

This is indeed the case, as illustrated in Figure 6, althoughnote that readout need only be partially destructive, asignificant factor that is discussed below. In writing a ONE,the target base is switched to zero volts, so that allZERO-state mucaps are made positive with respect to thegate metal. As explained above, bombardment with theprimary beam will set these elements to the gate metalpotential. Reestablishment of the bias of -50 V on the baseelectrode will than pull these elements down to the negativecondition shown in Figure 5(a). A tabulation of operationsis shown in Table 2. Two different times, tw and tr, aregiven for the writing and reading operations respectively,since a writing operation requires more charge to bedelivered to the target than the reading operation. Thealtemative to varying the read and write times is to adjustthe beam intensity. Either method may be used. For aplatinum secondary emission surface having a secondaryemission coefficient of 1.6 at 2 kV, and using an electronbeam having a current density of one ampere/cm2, thewriting time should be approximately 0.5 ,us per bit. Sincereading the target requires only that the stored charge

Ne

0

V1 (-40 V)

VBO (-50 V)

'1' STATE

0

VBO

BEAM ON

Vo (2 V)

VBO

'0' STATE<

Ow

VI

(a) WRITE ZERO

0

vo (2 eV)---

VBO (-50 V)

'0' STATE

0

2 VB +V0

VB1 = OV

n

,/ (Ne < n.)

0

VB1 0 V

SWITCH BASE BEAM ON

Figure 6. Writing Sequences for ZERO's and ONE's

36

2 Vo + V1

az <

0<V-

IL~lTiV1

0

v1 (-40 V)

VBO (-50 V)

'1' STATE

(b) WRITE ONESA-1 778-5

COMPUTER

000000 0

00000000

BEAM POSITIONS

09 009 000

INDIVIDUALO O OO OOMUCAPS

000000000 SA-1778-6

Operation Target Bias

Write ONE 0Write ZERO -50 VRead -50 V

Figure 7. "Quasi-Elements"

0

00cCO03()O1 0 1 1

0 0 0

MFM ENCODEDRECORDING

SA-1 778-9R1

Figure 8. Bit Storage and Encoded MFM Recording

should be sampled, it is possible to use very much shorterpulses than for writing. Although not yet demonstrated inour laboratory, it is believed that reading rates between 10and 100 MHz will be easily obtained in a single tube.

Target Usage

As mentioned in the introduction, the target is used inthe so-called quasi-continuous mode in which each bit is

represented by the charge stored in a number of individualmucaps. Bit storage is illustrated in Figure 7. In this case, a

group of approximately nine mucaps is used to store eachbit. The presence of one or two defective mucaps does notaffect target operation. In the system delivered to the AirForce, each bit location is addressed randomly. Thedeflection system is allowed to settle at a particularlocation, and then the beam is tumed on to interrogate thecharge stored at that target position. When operating in thismode, it is desirable to have a reasonable guard area aroundeach stored bit. However, it is highly probable that mostEBAM systems will be used in a block-oriented mode andthat information will be written as an encoded string oftransitions along a continuous path. Random access to thestart of the track would be achieved digitally, and the trackitself scanned on the fly, with the beam left on

continuously. This is illustrated in Figure 8. The upper partof the figure shows a data pattern written as a string of

individual bits, and the corresponding charge pattern. Thelower part of the figure shows the same data written usingMFM encoding. Note that ONEs are represented by atransition (in either direction), and ZEROs by the lack of atransition. Where there is a string of ZEROs, transitions areplaced between bits in order to assist in timing the data out.

As mentioned earlier, reading partially destroys thestored information. A succession of reads on ONE-stateelements will convert them into the ZERO state. Thisoccurs as illustrated in Figure 9, which shows the dischargecurve from the ONE state into the ZERO state as afunction of the number of reads. In the present system onlya single comparator level is used to distinguish betweenONEs and ZEROs. The problem of refreshing the data issolved by incorporating a second comparator level asindicated in the figure. Pulses falling in the region betweenLevels and 2 would then logically be assigned as a ONE,but would cause refresh of that particular piece of databeing read. The incorporation of an automatic refreshtechnique has several implications for this type of memorytube. First, approximatley 100 reads without rewriting theinformation has already been demonstrated in thelaboratory, and a simple calculation based on a I0-Mbitread rate indicates that several thousand reads should beobtainable for every write. The second factor arises becauseelectrostatic charge storage is somewhat volatile. Earlystorage targets- show several hours of storage and it wouldappear possible to obtain storage times of several days in

February 1975 37

Table 2. List of Operations

Beam On

twtwtr

B 1

BIT. STORAGEC

NUMBER OF READS

A'/iZERO A\V2

/ 1- |_ LEVEL 1ONE BUT REFRESH

--- LEVEL 2

ONEI

)ISCHARGE CURVE

SA-1 778-1 5R1

000,000000 0000000000000000, 0000000 000000000000 0000,0000 0000000000000

000000000000000000000000

Figure 10. Eliminating Long-Term Drift by Periodic Refreshing

production. Indefinite information retention can beachieved by ensuring that the complete memory is readperiodically and therefore is automatically refreshed. Theautomatic refresh technique also enables us to correct forlong-term drifts in the system since misalignment betweenthe reading beam and the stored information will cause adecrease in ONE-level output. Refresh repositions the dataunder the drifted beam position as illustrated in Figure 10.The actual time required between refresh will be governedby many factors including system drifts, target volatility,and bit interference effects. The latter can be caused whenneighboring tracks of information are read repeatedly orrewritten frequently, since the cross section of the writingbeam will nearly always be gaussian in shape; the tails onthe spatial distribution cause the interference effects. Ifeven larger quantities of information are to be stored in asingle tube in the future, it will probably be necessary toincorporate some fiducial mark system for locating thedata. The need for this referencing system will probablyarise between 107 and 108 bits per tube. Several schemeshave been proposed at SRI, but not implemented. RCA hasdeveloped one technique, also under Air Forcesponsorship.

38

REFRESH PATH(After Small Drift)

ORIGINALWRITINGPATH

SA-1 778-7

The Storage TubeThe design goal for the first fully operational system is

4 X 106 bits per tube on a target 1.8 cm X 1.8 cm, or a bit-spacing of 8 gim. Access time to any address is to be lessthan 3,s. The complete tube assembly as delivered to theAir Force is illustrated in Figtire 11. It is made using a veryprecise erector set type of construction that permits a greatdeal of flexibility for making changes in the laboratory. Theelectron optical components are mounted on support rings,which are held together by three 0.5-inch diameter rods.The gun is at the bottom; next are the lens, the deflector,the readout analyzer, and the target plane.

Details of the actual storage target plan are shown inFigure 12. This plane can hold two 0.25-inch storagetargets, one placed on either side of the center axis. In thisfigure one target has been removed to show the mountingholes.

The required access time, address accuracy, and freedomfrom beam distortion are determined by the deflectionsystem. This comprises an octupole deflector' and theassociated electronics. The octupole deflector (Figure 13)used in present systems offers significant advantages over

COMPUTE R

ZERO

ONE _

Figure 9. Readout Technique Using Automatic Refreshing

Figure 12. The Storage Target Plane

Figure 13. The Octupole Deflector

4 5 6

I, ,I,1 ~11

Figure 11. The Electron-Optical Bench

February 1975

0 1 2

I , I3

39

more conventional deflectors. It consists of eight electrodesarranged symmetrically about the beam axis. Unlikeconventional two-stage deflectors, the octupole x and ydeflectors share a center of deflection and have equalsensitivities. This is achieved by compounding thedeflection voltages in the form Vx + kVy, where k is anumber between one and zero. The value of k controls thedistribution of the deflection field and is chosen to achieveoptimum performance.

The electron source used in this system is a thoriatedtungsten cathode. It is anticipated that production tubeswill use a barium dispenser cathode. The latter is relativelyinexpensive and has a quoted life of 50,000 hours at2 A/cm2.

The reader will note that all components areelectrostatic rather than magnetic, which allows simpler,less costly, and lighter construction. In addition, accurate,fast access can be obtained without hysteresis in the beampositioning.

In the future, a considerably simpler readout assembly isanticipated. All components and component toleranceshave been designed so that when testing is completed andwe are ready to build a prototype tube, only minormodifications to the basic electron optical components willbe necessary. Production tubes are expected to be about 12inches long and approximately 2 inches in diameter.

The Demonstration System

The main elements of the experimental unit delivered tothe Air Force are shown in Figure 14. This unit combines

all the components of a complete prototype system and isintended to provide a means of evaluating EBAMperformance under conditions close to that of an operatingmemory.

The single tube module is controlled by a standardMacrodata MD-100 memory exerciser. This exerciserproduces data pattems, addresses, and read/write com-mands in parallel. It also provides a means of comparingdata read from the EBAM with data written originally. Thedata, address, and operational commands are passed to aninterface unit where all the timing is determined. From theinterface, logic signals are passed to the actual control unitsthat switch the beam, provide the deflection voltages, anddetermine the target bias for reading and writing. In theexisting configuration, the memory exerciser limits thenumber of address locations to 65,536.

Addressing In the present system all addressing isachieved in random access. In the first production systems,block access is likely to be used, since such access permitsthe operating rate to be increased significantly. However,block access requires additional circuitry that has not beendeveloped. The 16-bit address word from the exerciser isdecoded into two 8-bit coordinates. These are then passedto the digital/analog converters and to the deflectionamplifiers, where the final deflection voltage is detennined.This part of the circuit is designed for full 12-bit capabilitywith a settling time of 3 ,us to the level of 0.01 percent. Thetime taken for this part of the system to settle withintolerance is termed the address delay. This is the controllingfactor in determining the random access time.

Figure 14. Electronics for I IEBAM Module System TA-720522-114

40 COMPUTER

IIII

Reading and Writing The reading and writing operationsare carried out by controlling the bias applied to the targetbase and the length of the beam pulse. Thus, the data to bewritten determine the bias during a write command (-50 Vfor a ZERO and 0 V for a ONE). During a read commandthe bias is set to -50 V. This bias is set at the start of thememory cycle, but the beam is not tumed on until theaddress delay has been completed.

Reading During a read cycle the signal from the readoutanalyzer is passed to an amplifier and then to a comparator,which is set to determine the binary condition. The data arethen stored in a buffer in the interface until they can bestrobed back into the exerciser and compared with whatwas originally written. If an error is encountered, a pulse ispassed to an extemal connector on the exerciser, fromwhich it can be accessed for counting purposes or used witha suitable display on an X-Y oscilloscope for error mapping.Typical readout signals for a train of alterante ONEs andZEROs are shown in Figure 15. These signals are as viewedafter amplification and just before the comparator circuit.

Performance and Conclusions

The complete demonstration system is shown in Figure16; the exerciser is at the left, the control unit is in thecenter, and the memory tube is concealed in its magneticshield on the right.

During system testing at SRI, the module has operatedquite satisfactorily. The most difficult problem was todesign a satisfactory readout amplifier. However, thesystem has now been operated up to I-MHz read rates, andit appears that 10 MHz will be easily obtainable in theblock-oriented mode. Some early measurements of errorrates appear extremely encouraging; e.g., an error rate ofless than I in 109 was encountered in the first system tests.

The major research remaining is that of target life. Atpresent, attempts to measure a real lifetime appear to bemasked by contamination of the medium surface. This isnot surprising since the demountable tubes currently in useare not processed or assembled in an ultra-cleanenvironment. It is also possible that the targets themselvesare not sufficiently clean before insertion into the tube. Inone experiment an exposure of 15 C/cm2 caused the signalto decay to its permissible limit. Assuming a 25-,u diameterbit and a writing efficiency of 0.5, and assuming a blockaccess mode of operation with uniform target usage, aI-MHz write rate and a 106 bit target, the life would thenbe five years. Since an improvement by at least one order ofmagnitude seems possible, a very respectable life may beanticipated.

Apart from actually proving that the medium can haveadequate life, there appears to be no major impediment tothe successful construction of a complete operating

Figure 15. Amplified Readout Signal

Figure 16. USAF EBAM Module

February 1975 41

SPIE takes a closer look atEffective Utilization & Application of,

SIMULATORS &SIMULATIONPresented By

The Society of Photo_Optical Instrumentation EngineersCOOPERATING ORGANIZATIONS

Ames Research Center,National Aeronautics & Space Administration

United States Naval Equipment CenterUnited States Army Electronics Command

March 17-18,1975Disneyland Hotel, Anaheim, California

Simulation techniques are applicable to a wide breadth oftechnical disciplines. These extend from mechanical andhydraulic systems to ultra high-speed computers, to laserholographic displays, and everything in between. Possiblythe most challenging area of simulation is the display of adynamically changing realistic scene because it involves largeamounts of informatibn. Of special interest to this seminargroup is the compilation and storage of visual data bases torepresent real-world scenes. The subsequent retrieval of thisdata and its manipulation and the display of the data forinterpretation has wide application for both training anddesign proofing.General Chairman: F. P. Lewandowski, The SingerCompany, Simulation Products Division.

COMPUTER GENERATED GRAPHICS FOR SIMULATIONChairman: S. Coons, Univ. of Utah.

A Brief Historical Look at Simulation: F. P. Lewandowski* Computer Generated Graphics (tutorial) W. S. Bennett,Singer, Sim. Prod. Div. * Development of a Large-ScaleOptical Simulation: E. M. Winter & D. P. Wisemiller, IBM,Fed. Sys. Div. * Animated Half-Tone Images: F. Parke,Case Western Reserve Univ. 0 B-Spljne Curves ahd Surfaces:R. Riesenfeld, Univ. of Utah * The Movement PerceptionProduced without Actual Target Displacement: K. Mizusawaand Shih-yung Chung, Penn. State Univ.REAL TIME SCENE GENERATIONChairman: H. Wolff, Tech. Dir., Naval Training Equip. Center.

Displays in Flight Simulation (tutorial) D. G. O'Connor,Singer -- Sim. Prod. Div.lmage Syntheses with ServoedCameras: D. Slater and M. Pettus,:Magicam, InceOpticalScanning Probe Technology (Tutorial): M. Shenker, FerrandOpt. Co., Inc.6Computer Image Generation System: M.Bunker, G. E. Ground Sys. DepteNight Calligraphic DigitalVisual System: W. L. Chen, Singer, Sim. Prod_ Div.Computer Generated Full Spectrum Calligraphic Color forPiloted Visual Simulation Landing Approach Maneuvers:W. D. Chase, NASA-Ames Rsch. Ctr.-Holographic CarrierLanding Simulator: A. H. Rodemann, Naval Trg. Eqpt. Ctr.IMAGE PICKUP AND DISPLAY DEVICESChairman: D. Ansley, Singer, Sim. Prod. Div.

Some New Solutions to the Depth of Field Problem inFlight Simulation Image Pickup Devices: A. M. Spooner,Redifon Fit. Sim., Ltd. and D. R. Lobb, Sira Inst. FieldSequential Color TV for Visual Simulation: A. Kaiser, CBSLabs.-Collimated Displays for Flight Simulation: A. M.Spooner, Redifon Fit. Sim., Ltd.eTelevision Projectors:H. C. Hendrickson and J. D. Stafford, Philco-Ford.-TheDevelopment of .Wide Angle Visual Display Systems atNorthrop: A. A. Gordon, D. L. Patton and N. F. Richards,Northrop Corp.eA Full Field of View Optical Display forAerial Combat Simulation: R. Heintzman, WPAFB, Aero.Sys. Div.*Measurement of Flight Simulator Visual SystemPerformance: R. B. Ewart and J. H. Harshbarget, WPAFB,Aero. Sys. Div.SIMULATION SYSTEMSChairman: J. Dusterberry, NASA Ames Rsch. Ctr. aNuclear Reactor Simulators: T. E. Hughes, Singer, Sim.Prod. Div. * Locomotive Simulation: W. Abmrose, AtchisonTopeka & Santa Fe Railway 0 UCLA Driving SimulationLaboratory: R. Kemmerer and S. Hulbert, UCLA, L.A.,R. J. Donohue, Env. Activity Staff, G. M. Corp. * FilmBased Visual Systems for Flight Simulators: A. Collier andP. Astley, Singer, Sim. Prod. Div.0

Special Effects at Disneyland: W. Bealer, Chf. Eng., Disney-land.0oPanel Discussion: Future Objectives of Simulation.Moderator: J. Dusterberry Panel: H. Wollf, D. Ansley andS. Coons. Reader Service Number 229

Yla For full proceeding and program informationcontact SPIE P.O. Box 1146, Palos Verdes

Estates, California 90274 Area 213 / 378-1216

memory. We believe that a complete memory system,including tubes, can be packaged in a single unit somewhatsmaller than the control unit discussed here.

Acknowledgments

The author of this paper acknowledges the support ofthe Memory Technology Group of the USAF AvionicsLaboratory.7 I would also like to thank J. S. Moore andP. R. Thornton for their help throughout the work, D.Limuti and J. Clark for their work on the electronics, andC. C. Hartelius and E. R. Westerberg for fabricating thestorage targets.

References

1. J. Kelly, J. S. Moore, and P. R. Thornton, "The Development ofan Experimental Electron-Beam-Addressed Memory Module,"Proceedings of the IEEE 1974 National Aerospace andElectronics Conference, p. 55.

2. -J. Kelly and J. S. Moore, "Electron-Beam Addressed MemoryResearch," USAF Avionics Laboratory Technical ReportAFAL-TR-74-176.

3. "High-Information-Density Storage Surfaces," L. N. Heynick,ed., Seventeenth Quarterly Report, ECOM 01261-17, ContractDA 28-043 AMC-01261(E), SRI Project 5444, StanfordResearch Institute, Menlo Park, California (October 1969).

4. G. W. Ellis, G. E. Possin, and R. H. Wilson, "Diode Detection ofInformation Stored in Electron-Beam-Addressed MOS Struc-ture," Applied Physics Letters, Vol. 24, No. 9 (1 May 1974).

5. M. S. Cohen and J. S. Moore, "Physics of MOS Electron-BeamMemory," J. Appl. Phys., Vol. 45, No. 12, pp. 5335-5348(December 1974).

6. F. J. Marlowe, "Silicon Target for Electron-Beam Memory,"USAF Avionics Laboratory Technical Report AFAL-TR-73-253.

7. "Electron-Beam MemoryF33615-72-C-1906.

Research," USAF Contract

John oeliy was born in Bristol, England on May18, 1936. He received the B.A. degree inPhysics from Cambridge University, England, in1959. He received an MSc degree in Physicsfrom London University in 1964 and an M.A.from Cambridge in 1966.

In 1966 he joined the Physical ElectronicsGroup at Stanford Research Institute in MenloPark, California, where he worked on electronoptics, electrostatic deflector design, and

information storage. He is currently head of the electron-beam-addressed memory (EBAM) program and was responsible for theprogram leading to delivery of an experimental EBAM unit to theUSAF in January 1974.

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