US2835845A - Electro-static methods of storing and recovering information - Google Patents

Electro-static methods of storing and recovering information Download PDF

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Publication number
US2835845A
US2835845A US422056A US42205654A US2835845A US 2835845 A US2835845 A US 2835845A US 422056 A US422056 A US 422056A US 42205654 A US42205654 A US 42205654A US 2835845 A US2835845 A US 2835845A
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United States
Prior art keywords
spot
potential
density
current
charge
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Expired - Lifetime
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US422056A
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English (en)
Inventor
George F Bland
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International Business Machines Corp
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International Business Machines Corp
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Publication date
Priority to IT532932D priority Critical patent/IT532932A/it
Application filed by International Business Machines Corp filed Critical International Business Machines Corp
Priority to US422056A priority patent/US2835845A/en
Priority to GB10058/55A priority patent/GB786520A/en
Priority to FR1141385D priority patent/FR1141385A/fr
Priority to DEI10074A priority patent/DE1015483B/de
Application granted granted Critical
Publication of US2835845A publication Critical patent/US2835845A/en
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Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/08—Cooling; Ventilating
    • H01F27/10—Liquid cooling
    • H01F27/12—Oil cooling
    • H01F27/14—Expansion chambers; Oil conservators; Gas cushions; Arrangements for purifying, drying, or filling
    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11C—STATIC STORES
    • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
    • G11C11/21—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements
    • G11C11/23—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using electric elements using electrostatic storage on a common layer, e.g. Forrester-Haeff tubes or William tubes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J31/00—Cathode ray tubes; Electron beam tubes
    • H01J31/08—Cathode ray tubes; Electron beam tubes having a screen on or from which an image or pattern is formed, picked up, converted, or stored
    • H01J31/58—Tubes for storage of image or information pattern or for conversion of definition of television or like images, i.e. having electrical input and electrical output
    • H01J31/60—Tubes for storage of image or information pattern or for conversion of definition of television or like images, i.e. having electrical input and electrical output having means for deflecting, either selectively or sequentially, an electron ray on to separate surface elements of the screen

Definitions

  • the present invention pertains to improvements in electro-static methods of storing and recovering information.
  • An object of the invention is to provide an improved method of producing effective differentiation between digits by controlled variation in the density of the primary electron beam used to effect storage and read-out.
  • a particular object is to provide a method of the above type utilizing a dual-density electron beam to store differing digits for use in binary number computational systems and the like.
  • a further object is to provide a method of the above type in which the length of time during which the electron beam must remain conducting is renderedshorter than in prior methods, whereby speed of operation and precision of the system may be increased.
  • Another object is to provide a dual density storage method of the above nature wherein distinction between differing digits may be achieved without requiring beamshift or double-spot bombardment for certain digits, thereby increasing the digit capacity of a given screen area.
  • a still further object is to provide a greater amplitude difference between the read-out signals for differing digits.
  • FIG. 1 is a diagrammatic illustration of a typical cathode ray tube equipped with a suitable pick-up plate for reading out stored digital impulses;
  • Figure 2 illustrates the behavior of a bombarded spot as similar to that of a space-charge-limited diode
  • Figure 3 is a curve showing the static voltage-current characteristics of the theoretical diode comprised by the bombarded spot and its environs;
  • Figure 4 is a graphical illustration of signal contrasting characteristics produced with low-density read-out of charges stored at low and at high sharp beam densities.
  • n is the number of significant figures.
  • thedecimal number 19 in asystem employing 5 significant figures may be written It will be seen that the above representation of 19 is derived by choice of a as either 1 or 0 in the various ,1.
  • the numeral 19' designates a cathode ray tube comprising an envelope 1i coated on itsinterior lateral portion with a conducting material 12 such as aquadag, and having its glass end screen portion 13 interiorly coated with a suitable, phosphor M.
  • the plate 15 hereinafter referred to as the pick-up or signal plate, is connected to the input conductor 16 of a signal amplifier 17', and also via a resistor 16:: to ground.
  • the tube l'll contains the usual cathode 18, control grid 19, focussing anode 21', accelerating anode 2%, and hori- Zontal' and vertical deflector plates 22 and 23 respectively.
  • Thegrid 19 is connected to and controllable by a suitable pulse generator and control network 24. Similarly, the cathode iil, anodes 21 and 22, and deflector plates. 22
  • the present invention is based on the behavior of a bombarded'spot on the target'of a cathode-ray tube as the-cathode of a space-chargelimited diode.
  • the anode of the theoretical diode comprises the-collector lining 1.2 of the tube ill, while the cathode is a spot-area-251 on the fluorescent screen 14. under bombardment by an electron beam 26.
  • Theei'fects taking place at and near the spot Zi may be set forth as follows, referring to diagrammatic Fig. 2:
  • the primary beam 26 strikes the spot 25 it supplies electrons: thereto, but duev to the phenomenonof secondary emission, it. also dislodges electrons from the target area. Some of these dislodged secondary electrons have sufficientvelocity toreach the grounded collector 12, Fig. 1, it e., anelectroncurrent-Iflows from the spot'to the collector.
  • mary electron velocity is such that the secondary emission ratio 6 of the target is greater than unity. Therefore, since for 1 primary electrons striking the target per unit of time, 61 secondary electrons will be released, and the primary beam current and collector current being equal as noted, there is an excess (61)I of secondary electrons which move back and forth between the target and some boundary 27 intermediate the target and collector. The transit time of these electrons is of the order of 105 seconds. These excess secondary electrons establish a space charge in the immediate vicinity of the bombarded spot, the boundary 27 of this charge being the point at which the lower velocity secondary electrons are forced to turn back while the higher velocity electrons have sufficient energy to escape to the collector, as illustrated in Fig. 2 by looped and straight arrows respectively.
  • the actual value of potential at the boundary 27 with respect to the bombarded spot is that which corresponds to the initial potential u of the secondary electrons whosevelocity is zero at the boundary, and is independent of the magnitude or density of the primary beam.
  • the number of electrons leaving the boundary 27 of the space charge equals the primary beam current. Therefore, the boundary 27 may be considered as comprising a virtual cathode in the diode, approximately hemispherical in shape, and located at a distance inversely dependent on the amplitude of the collector current.
  • a general method is to establish difiering values of static conditions at difiering locations on the target screen.
  • the spots are scanned with an electron beam.
  • the latter encounters the various spots it produces local potential pulses which differ in response to the differences in the previously established spot potentials.
  • These target pulses produce corresponding signals in the capacitatively coupled pick-up plate, in the present case the exterior plate 15, which latter pulses are sampled by the amplifier 17, amplified, and utilized in any desired computational manner.
  • Figure 3 illustrates the manner in which the static potential V of the spot 25 with respect to the collector 12 varies with different values of primary beam current density in the above described theoretical diode. It will be noted that at low values of current as at point A, the potential V is positive. This is due to the fact that the boundary 27 of the virtual cathode is at or beyond the collector so that the virtual cathode space charge fills the entire space between the spot and the collector. As the density of the primary .beam current is increased the potential of the spot 25 with respect to the collector decreases to zero and then becomes increasingly negative with larger values of current, as the limiting space charge within the virtual cathode .27 increases in density and decreases in radius. 7
  • the diode will not respond either upward or downward in accordance with its characteristic curve, Fig. 3, if the primary current rate of change exceeds a certain critical value, this value being determined by the rate at which the space charge can form within the diode.
  • the formation of the space charge is dependent on the capacities associated with the diode and the transit time of the secondary electrons. Assuming 4 this transit time of about 10- seconds, as previously noted, the maximum for consistent curve compliance may be taken about as 10 1 amperes per second, where I is the total current charge of the primary electron beam 26.
  • the target potential may then be left at any one of various values between .B and +A, depending on the rate at which the beam is turned off. If the turn-off is slow enough to allow the diode to adjust to each decreasing value of current, i. e., if the turn-off rate is less than the critical the spot 25 will be left with a charge equivalent to +A.
  • the turn-off is rapid the'spot will be left at a potential bring the spot potential to point B, as noted.
  • the current is normally turned on slowly enough .for the diode to adjust itself along its characteristic curve to B, regardless of whether the digit to be stored is 0 or 1. If 1 is to be stored, the current is turned ofi rapidly, leaving the spot 25 with a negative charge as described above. If a zero is to be stored the current is turned off slowly, i. e., at a rate well below allowing the diode condition to adjust itself back along the characteristic curve to point +A, thus leaving the spot 25 positively charged. 7
  • the spot 25 When the beam is subsequently turned on for reading, if the spot 25 is at or about potential +A, it proceeds from A to -13 along the characteristic curve, and since its motion is only in a negative-direction, an initially negative signal is induced in the pick-up plate.
  • the spot potential In the case of the negative or digit 1 charge on the spot 25, as the reading current is turned on slowly, the spot potential first moves in a positive direction toward point A, adjusts itself to the characteristic curve and then moves along the latter negatively toward point B. An initially positive signal is thus induced in the pick-up plate.
  • Bombardment in the second spot substantially removes the positive charge from the first portion of the dash, so that when this first portion is strobosccpically sampled under the reading beam, its output signal is distinctive from that of the single or Zero spot.
  • this method the speed of turn-on and turn-oil has relatively little effect on the ability to store information, but it shares the above noted disadvantage of comparatively slow speed, for while the turned-on time for a dot" may be about 1 microsecond, a dash requires approximately 5 microseconds.
  • a further disadvantage is the fact that the clashes require more room on the target, thus reducing the capacity for storage in a given area.
  • the method of the present invention instead of employin a single basic beam current density and relying on carrying the spot potential more or less gradually to difierent locations along the above-described characteristic curve to achieve distinctive digit charges, utilizes two distinct basic current densities applied siarply for short and substantially equal periods of time.
  • a fixed beam density of low value is employed to record a Zero, while a fixed high beam density is used to eilect a one recording.
  • These two densities are achieved by square-wave potential pulses respectively of low and high amplitude applied to the control grid 19, as indicated in Fig. 1.
  • the zero grid pulse may be of the order of 22.5 volts and the one pulse from 50 to 75 volts, it being understood, of course, that these particular values are given merely as examples illustrative of the method.
  • both turn-on and turn-0E are very rapid, i. e., the rates of change are greater than the critical Referring to Fig. 3, when the low density beam is initially turned on, the potential of the spot 25 quickly assumes a positive position A on the characteristic curve and remains there, as the fixed low beam current does not permit further progress up the curve. When the beam is turned off, the spot charge potential remains at or very close to +A.
  • the polarity of the stored charges is sensed by subjecting them to the same low density of beam 26 as was used in zero storage.
  • the charged spots are subjected to beam pulses controlled by the low-level grid voltage V as shown in the lower curve, the resulting efiects on the pick-up or signal plate appearing in the middle curve.
  • the upper curve illustrates the stroboscopic gating of the amplifier to sample the recorded data.
  • the low grid potential V is employed throughout, so that all reading is carried out at the low beam density.
  • the signal plate voltage characteristic follows the solid line, Fig. 4.
  • a strong positive pick-up signal S is sampled by the amplifier, the grid potential is raised from the low V to the high V immediately at the termination of the sampling period, as illustrated in dotted lines on the grid potential curve.
  • the target spot is subjected again to sudden bombardment at the high beam density, rewriting the negative charge condition as previously described.
  • the dotted line on the signal plate voltage curve illustrates the strong negative swing due to the formation of the heavy space cloud as the high beam density is applied, and the corresponding positive swing as the cloud disintegrates at the termination of the pulse. As these swings occur outside the sampling period t they produce no effect on the output of the device. In the case of zero recordings, no special regenerative grid control is necessary, since, as previously noted, the reading by the low density beam automatically maintains the positive spot charges.
  • the present method employs a fixed low beam density for positive charging, a fixed high beam density for negative charging, and preferably the same low density for reading. All entered pulses of either type are made with maximum sharpness both of turn-on and turn-off of the beam, and since there is involved no gradual self-adjustment of the local theoretical diode along the latters characteristic curve, the time necessary to deposit the required distinctive charge is minimized for both types of entries.
  • This bombardment time while naturally variable to some extent among cathode ray tubes of differing characteristics, may be, as 'an example, of the order of l microsecond or less for each type of entry.
  • the new method presents a highly advantageous increase in speed over the previously noted and various other related methods of the prior art.
  • a second advantage is improved contrasting amplitude and sharpness, of signals, due to the widely contrasting beam density levels and the short and sharp periods of beam conductivity.
  • the maximum difference of swing between dashes and dots is that provided by the potential u of the virtual cathode with respect to the bombarded spot, while the present method provides the much greater diflference between B, and +A, Fig. 3.
  • a third advantage specifically over the dot-and-dash method of recording is an obvious saving in space, with consequent increased recording capacity for a given target area.
  • the present method normally is operated at fixed recording beam focus, with similarly evident advantages over methods dependent on focusing and de-focusing.
  • Electro-static differential data storage technique for use with a cathode-ray tube having a dielectric target surface and a signal plate in capacitative relation to said surface, said tube having a characteristic critical time rate of space charge formation dt when said target surface is bombarded with a cathode ray beam of currelnt density value I, which includes the steps of sharply establishing at a time rate greater than said critical rate a cathode ray bombardment with a predetermined fixed beam density of relatively low current value I on an individual spot on said target surface, mtaintaining said bombardment in stationary relation and fixed focus on said spot throughout a predetermined short interval of time, sharply terminating said bombardment at a time rate greater than said critical rate, whereby a characteristic informational static charge of positive potential with respect to a ground potential associated with said plate may be deposited on said spot in capacitative coupling relation with said plate, sharply establishing at a time rate greater than said critical rate a cathode'ray bombardment with
  • Technique as claimed in claim 1 including the steps of successively subjecting said difi'ering deposited charges to an electron beam of the lower of said two predetermined fixed densities, said beam being applied to each of said spots in stationary relation throughout a predetermined short time interval, whereby characteristically differing signals may be produced in said capacitatively coupled signal plate, and detecting said characteristically differing signals.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Hardware Design (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Image-Pickup Tubes, Image-Amplification Tubes, And Storage Tubes (AREA)
  • Measurement Of Radiation (AREA)
US422056A 1954-04-09 1954-04-09 Electro-static methods of storing and recovering information Expired - Lifetime US2835845A (en)

Priority Applications (5)

Application Number Priority Date Filing Date Title
IT532932D IT532932A (en(2012)) 1954-04-09
US422056A US2835845A (en) 1954-04-09 1954-04-09 Electro-static methods of storing and recovering information
GB10058/55A GB786520A (en) 1954-04-09 1955-04-06 Electro-static methods of storing and recovering information
FR1141385D FR1141385A (fr) 1954-04-09 1955-04-08 Perfectionnements aux procédés électrostatiques d'emmagasinage et de decupération de l'information
DEI10074A DE1015483B (de) 1954-04-09 1955-04-09 Verfahren zum Speichern von Angaben mittels einer Kathodenstrahlroehre mit Sekundaerelektronen-Sammelelektrode

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US422056A US2835845A (en) 1954-04-09 1954-04-09 Electro-static methods of storing and recovering information

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US2835845A true US2835845A (en) 1958-05-20

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US (1) US2835845A (en(2012))
DE (1) DE1015483B (en(2012))
FR (1) FR1141385A (en(2012))
GB (1) GB786520A (en(2012))
IT (1) IT532932A (en(2012))

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL290399A (en(2012)) * 1962-03-19

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2642550A (en) * 1950-01-19 1953-06-16 Nat Res Dev Electronic information storage device
US2671607A (en) * 1948-10-13 1954-03-09 Nat Res Dev Electronic digital computing apparatus
US2675499A (en) * 1948-07-10 1954-04-13 Bell Telephone Labor Inc Cathode-ray device

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR820870A (fr) * 1936-04-20 1937-11-20 Fernseh Ag Commutateur à rayon cathodique

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2675499A (en) * 1948-07-10 1954-04-13 Bell Telephone Labor Inc Cathode-ray device
US2671607A (en) * 1948-10-13 1954-03-09 Nat Res Dev Electronic digital computing apparatus
US2642550A (en) * 1950-01-19 1953-06-16 Nat Res Dev Electronic information storage device

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IT532932A (en(2012))
GB786520A (en) 1957-11-20
DE1015483B (de) 1957-09-12
FR1141385A (fr) 1957-09-02

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