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515

Use of an On-Line Computer

in Neutron Time-of-Flight Measurements
NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards ' was established by an act of Congress March 3, 1901. Today,

in addition to serving as the Nation's central measurement laboratory, the Bureau is a principal

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UNITED STATES DEPARTMENT OF COMMERCE

Maurice H. Stans, Secretary

NATIONAL BUREAU OF STANDARDS Lewis M. Branscomb, Director

NBS TECHNICAL NOTE 515

ISSUED JANUARY 1970

Nat. Bur. Stand. (U.S.), Tech. Note 515, 31 pages (Jan. 1970)

CODEN: NBTNA

Use of an On-Line Computer

in Neutron Time-of-Flight Measurements

H. T. Heaton II Nuclear Radiation Division

Center for Radiation Research

National Bureau of Standards

Washington, D.C. 20234

NBS Technical Notes are designed to supplement the Bureau's regular publications program. They provide a means for making available scientific data that are of transient or limited interest. Technical Notes may be

listed or referred to in the open literature.

For sale by the Superintendent of Documents, Government Printing Office

Washington, D.C, 20402 - Price 35 cents
CONTENTS

Page

1 . INTRODUCTION 1

2. COMPUTER CHARACTERISTICS 1

3. EXPERIMENTAL ARRANGEMENT. 7

4. CONCLUSION 12

5. REFERENCES 12

APPENDIX A. COMPUTER PROGRAMS 13

A. 1 . Interrupt Programs 15

A. 2 . Board Programs .

.

18

li
Use of an On-Line Computer in Neutron Time-of -Flight Measurements

H. T. Heaton,II

This paper describes the on-line data handling system at the NBS Electron Linear Accelerator facility as it

is used for measuring neutron total cross sections by timeof-flight techniques.

Key Words: Data handling system; interruptable computer;

neutron time-of-f light ; neutron total cross

sections; Program Selector Board; on-line

computer.

1. Introduction

In the last few years, the use of on-line computers for gathering

data in nuclear physics experiments has become commonplace. There are

several reviews [1,2] on the general functions an on-line computer system can perform. The general philosophy of the on-line computer system

at the NBS Electron Linear Accelerator (linac) facility has been described previously. '[3-5] A detailed explanation of one of the experimental programs (Neutron Time-of-Flight) which routinely uses this computer

will be given in this paper. The paper will describe what signals from

experimental equipment are sent to the computer, how the computer uses

this information to make decisions depending on the signals, and what are

the limits and capabilities for this on-line system.

The first part of the paper will describe the physical characteristics

of the on-line computer and its associated hardware. The second section

will describe the Neutron Time-of-Flight project and its use of the computer. The appendix will be more specific and will describe computer

programs used to gather and monitor the experimental quantities.

2. Computer Characteristics

The on-line computer used at the NBS linac is an SDS-920. It has a

16K word memory, each word having 24 bits. The machine cycle time is 8 jxs

with a typical machine language instruction of 2 or 3 cycles. The registers available to the programmer are the main accumulator, an extended

accumulator for the least significant portion of double length words, an

index register, and a 14 bit register containing the address of the current instruction.

1 Figures in brackets indicate literature references at the end of this

paper.
The SDS-920 is a real time computer with interrupt capability. The

80 levels of priority interrupts have led to a modular concept of both

hardware and software in a system called ROMEO [3-5] (Real time, On-line,

Modular, Experimental, Operator). Since I/O operations in the FORTRAN

compiler available for this computer are not interruptable, all programs

for the ROMEO system are written in machine language.

There are two types of machine language programs, Interrupt and Board,

Both types of programs may have a region of memory following the main body

of the program which is a data field. By means of the Program Selector

Board (PSB) any Board program (referred to as the subject program) may

operate on the data field of any program (referred to as the object program). Further discussion of Board programs necessitates a description

of the Program Selector Board, and hence will be postponed to later in

this section.

Interrupt Programs are used to record experimental data as it is

presented to the computer. The order in which the Interrupt programs are performed is determined by the value of the linkage table associated with

the particular Interrupt program. The Interrupt programs used in Timeof-Flight experiments are given in Table 1. The highest level program is

indicated by 0. Increasing value of the linkage table means lower priority

for the Interrupt program.

The interrupt capability of the computer is accomplished by testing

for an active signal on the interrupt interface after each machine language instruction. If the new interrupt is of a higher priority than the

one associated with the program in operation, the higher level program

will be performed before the lower level program is completed by having

the computer branch to the location in memory (given in the linkage table)

of the higher level program. If the computer is not carrying out a program, it returns to a "wait loop" (a set of instructions branching back

to themselves) and awaits the next interrupt.

The modular concept of programming has proved very useful. It prevents duplication of effort among the various experimental groups using

the computer. Modular programs, as opposed to one program which would perform the entire experiment, are of use when new equipment is added, as only

programs for this new equipment must be written, instead of rewriting one

long program. A compromise between loading all of the modular programs

each time the experiment is performed and one long program to carry out

the experiment is made by loading the programs, and then making a dump of

the memory with a self-loading bootstrap. The master tape thus produced

is then loaded at the beginning of each experiment. If there are any new programs to be loaded, or any priorities to be changed, this can be done

at this time.

The computer hardware built at NBS also has a modular concept. The

experimental hardware includes: 4 Program Selector Boards, 16 Analog to

Digital Converters (each with selectable number of channels up to 512),

4 scalers, 8 Digital Volt Meters, 3 Digital Register Units (24 line
Table 1 Interrupt Programs

00 MT Master Timer

01 RT Increment Data

02 RT Increment Data

03 RT Increment Data

04 RT Increment Data

05 RT Increment Data

06 TC 4100 Time Channels

07 SR Start Rate

10 SQ Coincidence Rate

11 TN Tube Noise 1 12 TM Tube Noise 2 13 TL Tube Noise 3

14

15

16

17

20 RT Increment Data

21 RT Increment Data

22 RT Increment Data

23 RT Increment Data

24 RT Increment Data

25

26

27

30 HP PBS 4-1

31 HD PBS 1-1

32 HQ PBS 4-2

33 HE PBS

34

35

36

37

50 HR PBS 4-3

51

52

53 HF PBS 1-3

54 HS PBS 4-4

55 HG PBS 1-4

56

57

117 HC Delete

All linkage locations not explicitly given are loaded with Increment

Data (RT) to insure that all interrupt levels have a program associated

with them.

3
Table 2

Board Programs

00 10 Zero Word 40

01 LB Clear 41

02 YL Type Line of Data-Y-Buf. 42

03 YC Type 4 Carriage Returns Y-Buf

.

43

04 YE Type 4 Carriage Returns W-Buf. 44

05 RP General 17 Punch 45

06 46

07 RA Paper Taper 47

RG Ratio-Y-Buf.

IA

IA

Scaler Save

Scaler Save

10

11

12

13

14

15

16

17

20

21

22

23

24

25

26

27

ID Type Data Message- W-Buf.

YD Type Data Message -W-Buf.

TL Type Line of Data-W-Buf.

TW List Sequencer

10 Decimal Type In- W-Buf.

IE Store Message

IC Load Data Field-W-Buf.

RT Paper Tiger

SA Scope (Control Room)

CZ Sum

K0 One Word Sequester (Scaler 3)

K0 One Word Sequester (Scaler 4)

50 QB Read Residuals

51 QC Read Residuals

52 QD Read Residuals

53 EU Clear Scaler, 2, 3, 4

54 LX List Collector

55 NR Run Number Increment

56 ON Group Enable 6 On

57 OF Group Enable 6 Off

60 SD Scope (Counting Room 3)

61 MB 64 Word Simple Operations

62 MD 256 Word Simple Operations

63 LI Smooth

64 KM 4100 Block Sequester

65 KN 256 Block Sequester

66 K0 One Word Sequester (P2)

67 K0 One Word Sequester (SEM)

30 CX

31 CX

32 CX

33 CX

34 CX

35 CX

36

37

IA

IA

Ratio Loader

Ratio Loader

Ratio Loader

Ratio Loader

Ratio Loader

Ratio Loader

Scaler Save

Scaler Save

70

71 HD List Loader (1-1)

72 HP List Loader (4-1)

73 HF Sequencer (1-4, 40)

74 HK Sequencer (4-2, 77)

75 HR Sequencer (4-4, 77)

76 HC Linkage Lister

77 HA Loader
parallel input), and a 60 Hz clock. Other equipment interfaced to the

computer includes a Time Interval Meter (TIM), and a high precision

digital voltage meter. The input/output hardware includes: 4 oscilloscope displays, an x-y plotter, a paper tape punch, a photoreader, a light pen, a typewriter and a teletypewriter.

The digital output from the experimental hardware is transferred to

the computer via the Multiplex Register Unit (MRU). When the point in an interrupt program is reached where the information from a piece of

equipment is needed, the instruction "Energize Output" (EOM) is used to

bring this information into the MRU. The instruction "Parallel Input"

(PIN) will then bring the contents of the MRU into computer memory. The

address portion of the EOM instruction determines which piece of equipment is interrogated. In addition to interrogating equipment, the EOM

signals can be used to initiate another program, increment a stepping

motor, open a relay, etc.

All peripheral counting equipment used in the time-of-f light experiments can be turned on or off simultaneously by means of the Group Enable

(GE) by gating the device with the GE signal.

The manipulation of the data in the Interrupt data field is accom- plished by Board programs. The Board programs used in the Time-of-Flight

experiments are given in Table 2. Similar to Interrupt programs, the means

of entering Board programs in the computer memory is through a linkage

table. For Board programs, however, the value of the linkage location

is used only as an identifier, and does not establish a program priority.

Since Board programs may operate on any data field, the device which

informs the computer which Board program to perform, and on which data

field that Board program should operate, is the Program Selector Board.

A typical PSB is shown in figure 1. Each Program Selector Board

:ontains 4 sets of thumbdials used to manually set up a control word

jhich the computer is programmed to read in upon command. The maximum

configuration of a set of thumbdials is 17 77 1177 77. The 10 dials

divide up the 24 bit word of the computer with a 7 on a dial occupying

bits of the word and a 1 on a dial occupying 1 bit . Labeling the

dials from 1 to 10, the computer word is divided as indicated: Dials 9,

10 correspond to the octal value of the Board linkage table location of

the subject program, dials 6-8 give the octal linkage location of the

object program, dial 5 indicates whether the object program is a Board

program CO) or an Interrupt program (1), dials 1-4 are used to control

internal options in the subject programs. After setting the thumbdial

to the appropriate values, the Board program is initiated by the SINGLE

CYCLE button, REPEAT CYCLE switch (60 Hz) or the EXT CYCLE input. This

initiates an Interrupt program which reads the control word on the set

of thumbdials and then makes certain logical checks. These logical

checks include whether the WBuffer or YBuffer is in use, if the subject

program is loaded, if the object program is loaded, and if the subject

program is currently in use. If a check should fail, the REJECT light

and appropriate function light are lit. If the logical tests are passed,
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sets of thuubdials on the Program Board Selectors used to call Board

Program (see text).
the interrupt control program branches to the Board program and executes

it. When the Board program is completed, the interrupt control program

sends an EOM signal over the PROGRAM COMPLETE BNC. This in turn can be

fed into the EXT CYCLE connection to initiate another Board program. On

the PSB are 3 switches (labeled SKS) which can be used to control yes/no

options within the Board program.

3. Experimental Arrangement

The Neutron Time-of-Flight group at the NBS electron linear accelerator performs two major types of experiments, the measurement of photoneutron cross sections and the measurement of neutron total cross sec- tions. [6-8 J In both cases a neutron spectrum produced by the 2 nano- second linac beam pulse is recorded. In the photoneutron experiments,

the linac electron beam passes through a thin radiator producing a bremsstrahlung pulse which strikes the target under investigation. In the

total cross section measurements, the electron beam is allowed to strike

a target directly. In this case the neutron spectrum produced furnishes

the "open" spectrum necessary for making a transmission measurement. The

"sample in" spectrum is obtained by inserting the element to be measured

in the neutron flight path. When corrections have been made for background

and dead- time effects, the ratio of the sample- in to sample-out counts in

channel i is the transmission, T^, of the element, in the ith channel.

This is related to the total cross section, o^, by

T. = e

_nCTi (1)

where n is the atoms per square cm of the sample.

Although the results of these two experiments are quite different,

all of the electronic equipment, and most of the on-line computer programs, can be used for either measurement. To date, only survey work has been

done on photoneutron experiments, and hence the remainder of the paper

will deal explicitly with the total cross section measurements.

The neutron energy range of interest for these measurements extends

from about 500 keV to 15 MeV. Two events occur when the electron beam

strikes the neutron target: neutrons are produced and an intense beam

of gamma rays, the gamma flash, is produced. The energy of the neutrons

is determined by the difference in time between the start and stop signals. The start signal is provided by the signal induced in a phototube

by the gamma flash. The neutrons travel over an evacuated, collimated,

40 meter flight path and are detected by a liquid scintillator. The

light produced by the proton recoil in the scintillator is detected by

three photomultiplier tubes. The coincident output (to eliminate tube

noise) provides the stop signal.

The major piece of equipment for a time-of-f light experiment is the

instrument measuring the time between the start and stop signals. For

these measurements a Time Interval Meter (TIM) digitally measures this

difference in nanosecond steps or channels. This digital output of the
TIM (total number of nanoseconds) is recorded in a 4096 word data field

of an interrupt program in the computer.

Converting eq. (1) to the experimental quantities measured, the neu- tron total cross section, in barns, for the Ith nanosecond time channel is

o-(l) = UMC. (D/N C (I))]/n (2) L in out

where C. (I) is the number of counts in channel I of the sample in speci n trum, C (I) is the number of counts in channel I of the sample out spectrum, N is a normalization factor for different amounts of total electron

beam charge between the sample in and sample out runs, and n is the atoms

per barn of the sample.

If the cross section as a function of energy rather than time is

desired, the neutron kinetic energy associated with the Ith time channel

is given by the relativistic expression

l _L

,l-[(L/c)/T(i: HI)- 77-T-V,-7TTj) "lj (3)

where, in appropriate units, L is the flight path length, c is the speed

of light, and T(I) is the time-of -flight of the neutron. For the one nanosecond channels of the TIM, and by recording the gamma flash with

the stop detector and observing in which TIM channel it occurred (GFC),

and knowing the time in nanoseconds it takes light to travel over the

flight path (L/c), the time-of -flight can be expressed in terms of any

TIM channel I by

, T(I) = (L/c) - GFC+I (4)

Figure 2 is a block diagram of the equipment used in neutron total cross section measurements. The major signals recorded by the computer

are shown. The computer input signals are indicated by I and the level

of the interrupt program associated with the signal by the subscript.

These subscripts, and all other numbers referring directly to the computer, or to computer programs, are in base 8 unless stated otherwise. The slow

electronics necessary to send logic signals to the computer are not shown

in figure 2.

There are three main methods of monitoring the linac beam current.

First the beam passes through a Secondary Emission Monitor (SEM) mounted

in the beam handling system. The output of the SEM, which is proportional

to the amount of charge in each beam pulse, is recorded by a current integrator. The gamma flash produced by the electron pulse from the linac

when it strikes the neutron target is monitored by an NBS P2 ionization

chamber. [9 J The output of the P2 , proportional to the energy in the

beam passing through the neutron target, is also recorded by a current

integrator. The integrator has a meter for reading the average current,
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and has a pulsed output, the rate of which is proportional to the meter

reading. The output of the integrator is recorded by the computer. The

third monitor is a small liquid scintillator mounted in the room containing the neutron target' and measures the average number of neutrons produced.

The total number of neutrons counted by the stop detector is also

monitored. The total number of neutrons counted will be less than the sum of the neutrons in the spectrum due to the fact that the TIM can only

count one neutron per linac pulse. This means there is a dead time cor- rection which must be applied to both the sample in and the sample out

spectra due to this one count per burst limitation. If s is the total

number of start pulses, and 0^ is the observed number of counts in

channel i, then the number of dead time corrected counts in channel i, C.

is

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These dead time corrected counts should be used in calculating the cross section given in eq. (2).

The highest priority program is one which counts 60 Hz pulses during

the entire time GE is on, i.e., as long as data are being taken. After

this program determines that 20 minutes have elapsed, it sends an EOM

signal which in turn initiates a program which types out the ratios of

SEM/P2 counts, total neutron/P2 counts and total neutron/neutron monitor

counts. These ratios provide a running check on the stability of the

experiment. If they are not consistent, the experimenter (rather than

the computer) can stop the run.

For the remainder of the tests performed by the computer monitoring

experimental conditions, the computer automatically terminates the run

if the test fails. The experimenter is informed by having one of the

spare lights on the psb lit indicating which test failed.

In addition to providing a time zero signal for the TIM, the start

signal performs several other functions. The total number of start

pulses are counted for the entire run for use in calculating the dead

time correction given by eq. (5). Since the number of start pulses is so critical in making the dead time correction, a test is made every

second to insure that the proper number of starts is being recorded. If

the correct number is not being recorded, the computer automatically

terminates the run. The start signal also initiates several delayed

gate generators, which are used to examine various time portions of the

neutron spectrum.

10
In order to reduce time slewing due to the finite rise time of the

phototube pulse, the anode signals are fed to zero crossing discriminators. [10] The output of each of the cross overs is split, with one output signal going to a "STROBED COINCIDENCE" circuit. The common input ("Strobe") to this circuit is the signal from a delayed gate generator

set to open between linac beam pulses. This allows the phototube noise

rate to be measured between pulses. This rate is an indication of phototube stability. [1.1] Every five seconds, the computer tests to insure

that the noise rate is within predetermined limits. If it is not, the

computer automatically terminates the run and informs the experimenter.

The other output of the zero crossing discriminators goes to a 2-out-of-3

AND GATE [12] which is used to eliminate phototube noise signals between

the three phototubes. The output of the 2-out-of-3 AND GATE is also split,

with one output signal going to the remainder of the conventional fast

stop electronics. (A more detailed description of the electronics is in

preparation for publication.) The other output of the 2=out-of-3 AND

GATE is recorded for one second. Hie computer then tests whether the

number of counts is greater than some lower limit. If the limit is not

exceeded, it indicates that one of the zero crossing discriminators has

failed, and again the computer automatically terminates the run and informs the experimenter.

The signal out of the stop electronics is also split. Part of the

stop signal is gated with the signal from a delay gate generator set to

allow neutrons with energies between 500 keV and 15 MeV to be recorded

by the TIM. If no stop signal was detected during the period of the

delayed gate, an artificial marker pulse is used to stop the TIM, and

reset it for the next machine pulse. The other part of the stop signal

is counted and used in the 20 minute ratios of the electron beam monitors

previously mentioned.

In addition to the first order dead time correction mentioned earlier, a second order correction may be necessary if the linac beam current

varies. To minimize this correction, a dual trip meter, driven by the P2

integrator, has its limits set so that when the beam current is not within ±10% of the average, a signal is sent which will turn off the Group

Enable. When it is necessary to correct for this second order dead time,

the output of the P2 integrator, recorded for 5 second intervals, is used

to form a profile of linac beam current distribution during the run.

At the end of a run all of the experimental information is punched

onto paper tape. This is then transferred to magnetic tape using another

SDS-920 computer. The magnetic tape is then used by the Univac 1108 at

NBS to make dead time corrections on each run; combine all of the samplein runs, sample-out runs, and background runs; normalize the total beam

charge for the sample in, and sample out runs; subtract properly normalized background; and for each channel, calculate the transmission, the

total cross section, the statistical error on the cross section, and the

neutron energy. The final form of data is available as a listing, on

cards, or as a plot.

11
4. Conclusion

This paper has shown the versatility of an on-line computer for

doing Nuclear Physics research by giving a detailed explanation of how

the Neutron Time-of-Flight experiments use such a system.

The main features of the SDS-920 computer used on-line were given.

The use of the interrupt capability of this computer for gathering data

from experimental equipment was described. Board Programs and their

initiation throughout the Program Selector Board were described as one method of manipulating the information in the data fields of Interrupt

or Board programs.

For those not familiar with the Neutron Time-of-Flight program being

carried out with the NBS linac, a description of the experimental arrangement was given. Included in this description was what signals the experimental apparatus supplied to the computer and how the computer was able

to use information to determine if the monitors were within preset limits

and if not to automatically terminate the run. By having the computer

monitor the experimental conditions the experimenter is relieved of

much of the routine data gathering and thereby is allowed to concentrate

on the experiment itself.

5. References

[1] Jones, J. A., IEEE Transactions on Nuclear Science, NS-14 , No. 1 576

(1967).

[2] Lidofskey, L. J., IEEE Transactions on Nuclear Science, NS-15 , No. 1 93 (1968).

[3] Broberg, J., Leiss, J., Schrack, R. A., and Wyckoff, J. M. , IEEE

Transactions on Nuclear Science, NS-11, No. 3 331 (1964).

[4] Broberg, J. B. , IEEE Transactions on Nuclear Science, NS-13 , No. 1 192 (1966). , [5] Wyckoff, J. M., IEEE Transactions on Nuclear Science, NS-13, No. 1 199 (1966).

[6] Schwartz, R. B. , Schrack, R. A., and Heaton, H. T. II, Neutron Cross

Sections and Technology, Proceedings of a Conference, NBS Special

Publication 299 771 (1968).

[7] Schwartz, R. B. , Schrack, R. A., Heaton, H. T. II, Bulletin of the

American Physical Society, Series II, 14 No. 4 494 (1969).

[8] Schwartz, R. B., Schrack, Ro A., and Heaton, H. T. II, A Search for

Structure in the n-p Scattering Cross Section, Phys. Letters, Vol.

30B, No. 1, 36-38 (Sept. 1, 1969).

[9] Pruitt, J. S., and Domen, S. R. , National Bureau of Standards Monograph 48 (1962).

[10] Whittaker, J. K. , IEEE Transactions on Nuclear Science NS-13 , No. 1 399 (1966).

[11] Lavole, L. , and Norton, R. , Nucl. Instr. and Meth. ,. 60 123 (1968).

[12] Whittaker, J. K. , Nucl. Instr. and Meth. 45 138 (1966).

12
Appendix A. Computer Programs

The appendix will explain how the computer performs some of the

tests, how data is gathered and manipulated, etc., by actually describp ing the machine language programs necessary for the on-line computer

for gathering data in a total cross section measurement.

Figure 3 shows all of the signals sent to and from the computer

during a typical measurement. (Indicated is the exact route of each

signal, although this is not pertinent for the following description.)

Signals sent to the computer terminate in one of the circles which indicate the priority level of the interrupt program used to process the

signal. Interrupt programs which send signals are indicated by having

the lines originate from one of the circles. The dotted lines originating from some of the interrupt programs indicate that the program from

which the line originates needs information contained in the interrupt

program data field on which the line terminates. The boxes labeled S. T. are shaping devices which allow the EOM signals to initiate other interrupt programs.

The machine language programs will be discussed in the same order

as they appear in the Interrupt and Board Linkage Tables given in Tables

1 and 2. With the computer loaded in this manner, 15K out of the 16K

memory cells are occupied. Two programs, however, (4100 Time Channels,

IPIC, and 4100 Sequester, BPKM) occupy slightly over 8K of memory due to

their 4K data fields. Most of the Interrupt programs are completed in

times of the order of 30 to 260 |is. The Interrupt program associated

with the TIM, however, takes 800 jis since it must do a decimal to binary

conversion for each piece of information recorded in its data field.

Since the Interrupt program associated with the PSB are lower priority

than the data gathering Interrupt programs, the amount of time it takes

to complete Board programs is not given.

Both in Interrupt and Board programs, the same program may serve several functions with only the quantity recorded in the data field being

different. In this case, after the program has been described only the

quantity recorded in the data field will be stated. Board programs may

transmit data to the typewriter over one of two buffers termed W and Y.

If the programs are the same except for the Buffer, they will be described only once. All programs are given four letter mnemonics, the first

two being either BP for Board programs or IP for Interrupt programs.

Hence only the last two letters of each mnemonic is given.

Complete documentation of all programs for the ROMEO system exist in

the Linac Radiation Division Office at the Center for Radiation Research,

13
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14
,If it is necessary to refer to another program in the description

of any program, the linkage location of the referenced program (prefixed)

by IP for Interrupt and BP for Board programs) will be given.

A. 1 Interrupt Programs

00 Master Timer (MT)

This program performs two functions. First, it records 60 hertz

clock pulses during the time GE is on to determine if the proper

amount of time has elapsed and the computer should monitor one of

the experimental parameters. This monitoring is accomplished by

the Master Timer Program sending an EOM signal which initiates

the monitoring program after the Master Timer program is completed.

The monitoring program interrogates the data field of the interrupt program actually recording the monitor output and then

determines whether the monitor is within proper limits. Every

second, the Master Timer Program emits an EOM 160 pulse initiating the programs Start Rate (IP07) and Coincidence Rate (IP10).

Every 5 seconds an EOM 164 pulse initiates the programs Tube

Noise-1 (IP11), Tube Noise-2 (IP12) and Tube Noise-3(IP13)

Every 20 minutes an EOM 347 pulse is sent initiating the "20

Minute Sequencer" (BP74). The second function of the Master

Timer program is to use the first 64 words of the data field to

form a profile of the short terra linac beam stability. This is

done by recording the contents of scaler 1 every 5 seconds, multiplying this number by 64 and dividing it by 500 (the maximum

number of pulses from the P2 integrator in 5 seconds), and then

using this as the channel address to increment by one.

01 Increment Data ( RT)

This program increments its data field by one each time it is

initiated. This is an example of one basic program which is used

to record different experimental parameters. This particular increment data program records the number of times scaler 2 reached

4096 counts, i.e., the overflows from scaler 2. To insure that

there is an interrupt program associated with every interrupt

level, the increment data program is loaded at all otherwise unused

levels. This prevents any spurious signal over an unused interrupt line from "hanging up" the computer.

02 Increment Data (RT)

See IP01. This program records scaler 3, "4096" counts.

03 Increment Data (RT)

See IP01. This program records scaler 4, "4096" counts.

15
04 Increment Data CRT)

See IP01. This program records P2 integrator counts.

05 Increment Data ( RT)

See IP01. This program records SEM integrator counts.

06 4100 Time Channels (IC)

This program brings the BCD word from the TIM into the computer

memory and tests whether the number in its BCD form is greater than

4096. If the number is greater, the program exits, and if it is

less, the number is converted to binary, and the appropriate word in

the 4096 data field is incremented by one.

07 Start Rate (SR)

This program sends out a warning if the proper number of start

counts are not being detected. Every second, the Master Timer program (IP00) initiates the Start Rate program, which in turn reads

the data field of IP20. If the number of counts read is less than

the value in the first word of its data field, the program sends out

signals to turn off the Group Enable, turns on light 375, and stores

the number read in the second word in its data field. Independent

of the value of the data word read, the program clears the first

word of data of IP20.

10 Coincidence Rate (SQ)

Every second this program monitors the number of coincidence counts

from the stop detector. It is very similar to Start Rate (IP07) but

with two exceptions: the data field read is IP21, and, if there is a failure (no coincidence counts detected) a pulse is sent to turn

on light 376. IP21 counts the number of coincidence counts.

11 Tube Noise-1 (TN)

This program monitors the noise rate in phototube No. 1 between

machine pulses. It reads the data field of IP22. If the number

read is not greater than the first word in its data field and smaller

than the second word in its data field, signals are sent to turn off

the Group Enable, turn on light 377, and finally store the number

read in the third word of its data field. In all cases, the data

field of IP22 is cleared. This program is initiated by the Master

Timer Program (IP00) every 5 seconds. The numbers loaded into the

first two words in the data field (this can be done with BP72) are usually the noise rate at the start of the experiment ±20%.

16
12 Tube Noise- 2 (TM)

See IP11. This program monitors the noise rate in phototube 2.

The data field read is IP23„

13 Tube Noise-3 (TL)

See IPllo This program monitors the noise rate in phototube 3.

The data field read is IP24.

20 Increment Data ( RT)

See IP01. This program records the number of start pulses

„

21 Increment Data ( RT)

See IPOlo This program records the number of coincidence counts

22 Increment Data ( RT)

See IP01. This program records phototube 1 noise pulses.

22 Increment Data (RT)

See IP01. This program records phototube 2 noise pulses.

24 Increment Data (RT)

See IP01 . This program records phototube 3 noise pulses.

30 Program Selector Board 4-1 (HP)

This is the control program for the first set of thumbdials of the

Program Selector Board in Counting Room 3. The remainder of the

Selector Boards are given in their titles where 1-a and 4-a refer

to the ath set of thumbdials in the Control Room and Counting Room

3 respectively. See Section 2 for a further description of the PSB.

31 Program Selector Board 1-1 (HD)

See IP 30.

32 Program Selector Board 4-2 (HQ)

See IP 30..

33 Program Selector Board 1-2 (HE)

See IP 30.

17
50 Program Selector Board 4-3 (HR)

See IP 30.

53 Program Selector Board 1-3 (HF)

See IP30.

54 Program Selector Board 4-4 (HS)

See IP 30.

117 Delete (HC)

This program can be used to delete any Interrupt or Board program

from the computer memory, by pushing the DELETE button on the PSB

board in the Control Room, and then typing:

IP0006, IP //.

where 0006 is the linkage location of the Interrupt program to be

deleted. For Board programs, the IP is replaced with BP. After

the program has been deleted, DUN will be typed.

A. 2. Board Programs

If a Board Program uses dials 1-4 for controlling functions within

the program, there will be an asterisk after the linkage location. These

dials usually control the start location in a data field where some operation begins. Unless stated otherwise, the following convention will be

followed: the first word of the data field corresponds to dials 1-4

equal to 0, second word to dials 1-4 equal to 1, etc., i.e., the number

in dials 1-4 is the octal number less one of the start location. All

Board Program mnemonics begin with BP

00* Zero Word (10)

This zeros the word in the object data field corresponding to

dials 1-4.

01 Clear Data (LB)

Clears the entire object data field.

02* Type Line of Data - Y-Buffer (YD

This program types without sign, the contents of the data field

as decimal integers. This program types the first 10 words of

data in a single horizontal line, then the next 10, etc. Type

out begins at the location given by dials 1-4. The program can

be terminated at any time by setting SKS 1000 which is available

18
as a switch on the psb •

04 Type 4 Carriage Returns - Y-Buffer (YE)

This program types 4 carriage returns on the typewriter connected

to the Y buffer and exits.

05 General 17 Punch (RP)

This program will punch the object data field in a FORTRAN

compatible mode, 17. It will also read tapes made using a Fortran program punched in a 17 format. If Breakpoint 2 is

reset, this program will punch tape, and if it is set, it will

read paper tape. When reading paper tape, the program assumes

that the first word is the number of words to be read. After

each word is punched/read a test is made to see if Breakpoint 1 is set* If it is set, the program exits.

07 Paper Taper (RA)

This program will punch on paper tape the object data field in a binary form. If Breakpoint 2 is reset, the program will punch

tape, and if it is set it will read tape. Either of these operations can be terminated by setting Breakpoint 1.

10 Type Data Message - W- Buffer (10)

This program will type out the contents of the object data field

in a form such that each word in the data field is treated as if

it consisted of four typewriter characters. The object data field can be loaded in this form with the Load Data Field Program

(BP16). The message is typed from the typewriter connected to

the W-Buffer.

11 Type Data Message - Y-Buffer (YD)

Same as BP10 for Y-Buffer.

12* Type Line of Data-W-Buffer (TL)

See BP02.

13 List Sequencer (TW)

This program types the contents of the data field as if each

word in the data field corresponded to the ten dials on a PSB.

14 Decimal Type In (10)

This program will enter decimal integers into the object field

by means of the typewriter. The location into which the decimal

19
data is to be typed is given by

*10.

followed by a carriage return. Then the decimal integer is

typed

9999.

followed by a carriage return. If another number is typed, it

will be loaded into the next location in the data field. The

program is exited by typing a control character such as a space.

15 Store Message (IE)

This is a dummy program which has a data field into which a message of 80 typewriter characters can be loaded „ The Type

Data Message Programs (BP10 and BP11) operate on this data field.

16 Load Data Field (IC)

This program will enter typewriter characters into the object

data field until the data field is completely filled. This program can be used to load a message into the Store Message Program (BP15). In loading the message, first a carriage return

should be typed, then the message typed (including spaces to

fill up 78 characters), and finally, another carriage return is

typed.

22 Paper Tiger (RT)

This program can be used to make a new Master Tape of the con- tents of the computer memory. The program first punches a selfloading bootstrap. Then, all memory cells in the computer,

through the first unused cell, are punched.

24 Scope - Control Room (SA)

This program presents a CRT display of the object data field on

the oscilloscope in the control room,

25 Sum (CZ)

This program sums the contents of the object data field and stores

the result in its data field.

20
26 One Word Sequester (KO)

This program will copy the first word of the object data field

into its data field. The Ratio Program (BP40) can only operate

on the data field of Board programs, so it is necessary to

temporarily store the data field of an Interrupt Program before

it can be used for a ratio. This program provides temporary

storage for the counts recorded in scaler 3.

27 One Word Sequester (KO)

See BP26. This program, provides temporary storage for the

counts recorded in scaler 4.

30 Ratio Loader (CX)

This program will copy its two word data field into the first

two words of the object data field. Since the Ratio program

(BP40) requires that its data field be loaded with the linkage

location of the programs whose ratio is to be taken, this much

shorter program can be used to load the data field of the Ratio

program just before its execution. Stored in this program's

data field are the linkage locations of the programs for the

ratio of SEM counts to P2 counts for each 20 minute ratio.

31 Ratio Loader (CX)

See BP30. This program is for the 20 minute ratio of total

neutron counts to P2 counts.

32 Ratio Loader (CX)

See BP30. This program is for the 20 minute ratio of total neutron

counts to neutron monitor counts.

33 Ratio Loader (CX)

Same as BP30 but for entire run.

34 Ratio Loader (CX)

Same as BP31 but for entire run.

35 Ratio Loader (CX)

Same as BP32 but for entire run.

36 Scaler Save (IA)

This program reads the first word of the object data field, then

adds the number to its data field. This program is necessary to

21
preserve the sum of the counts accumulated in the scalers, since

the EOM pulse which reads the scaler residuals also clears the

scalers. This particular Scaler Save program records the number

of P2 counts.

37 Scaler Save (IA)

See BP36. This program records the total number of SEM counts.

40 Ratio-Y-Buffer (RG)

This program types the ratio of non-zero numbers, truncating the

result to three significant figures. If one of the numbers is

zero, the program types ERROR and exits. The linkage location

of the Board Program whose data field is to be the numerator, is

loaded into the first word of data of the Ratio program. The

second word of data of the Ratio Program is loaded with the linkage

location of the Board Program whose data field is to be the denominator. The form of the result typed out is

6543210/3271605 = 200.*E-2

This program will work only with Board programs. If the ratio

of data in an Interrupt program is desired, this data must be

temporarily stored in a Board program. The program types the

ratio over the teletype connected to the Y-Buffer.

46 Scaler Save (IA)

See BP36. This program records the total number of counts in

scaler 3.

47 Scaler Save (IA)

See BP36. This program records the total number of counts in

scaler 4.

50 Read Scaler Residuals - Scaler 2 (QB)

This program reads the residual counts in scaler No. 2. It adds

to this number, the number of times scaler No. 2 reached 4096

(i.e., scaler 2 overflows).

51 Read Scaler Residuals - Scaler 3 (QC)

See BP50. This program reads the residual counts in scaler 3.

The answer is multiplied by 8, as the program assumes that the

input to scaler 3 is a prescaler with a scale of 8.

22
52 Read Scaler Residuals - Scaler 4 (QD)

See BP50. This program reads the residual counts in scaler 4.

53 Clear Scalers 2, 3, 4 (EU)

This program clears the contents of scalers 2, 3, and 4.

54* List Collector (LX)

This program will collect words out of the object data field and

store them sequentially in its data field. Dials 3, 4 give the

number of words of the object data field to be transferred. To

start loading at the first word of the data field of the list

collector, set dial 1 to 1.

55 Run Number Increment (NR)

This program adds one to its data field each time it is initiated

56 Group Enable 6 On (ON)

This program turns on Group Enable 6.

57 Group Enable 6 OFF (OF).

This program turns off Group Enable 6.

60 Scope - Counting Room 3 (SD)

See BP50. For counting Room 3.

61* Simple Operation (MB)

This program will perform operations on the object data field

depending on the value of dials 1-4, and then store the results

in its 64 word data field.

Dial 1, 2 Dial 3, 4 Function

00 sequester a . -» a . oi si

01 accumulate a .+ a . -» a . oi si si

02 subtract object a - a -» a

c , . si oi si from subject

03 subtract subiect a .-a .-» a . c , . ~_ OI SI SI from object

04 first difference a . -a . -* a . oi+l oi si

23
05

06

07

10 k

11 k

12 k

J running sum 2 a . - a

i 01 S J i=l

set object data

to zero

a .- oi

set subject data

to zero

a .-* si

add constant a . + k

Ol

-» a . si

subtract constant a . - k

Ol

-* a . si

multiply constant a . * k

Ol

-» a . si

62* Simple Operation (MD)

See BP61. This program is a simple operation program with a 256 word data field.

63* Smooth (LI)

This program calculates 2

(C

i

+2 *C

i +Ci+ i

} /4 for each channel ii=2

Here, C. is the number of counts in channel i and N is the number

of channels. The number of times the data is smoothed is one more than the octal number in dials 1-4.

64 4100 Sequester (KM)

This program will provide temporary storage for the TIM data

field by transferring the TIM data to its data field.

65* 256 Block Sequester (KN)

This program is designed to be used with the 4100 Sequencer

(BP64) or 4100 Time Channels ( IP06 ) programs. This program will

transfer 256 word blocks of data from the object data field to

its data field. Which 256 word block of data is transferred is

determined by dials 1, 2 and is given below:

Dials Energy (Mev) 1, 2 Channels Energy (MeV) Dials 1, 2 Channels

00 1-256 10 2049-2304

01 257-512 130-30.1 11 2305-2560

02 513-768 30.1-13.9 12 2561-2816

03 769-1024 13.8-7.65 13 2817-3072

04 1025-1280 7.64-4.93 14 3073-3328

05 1281-1536 4.92-3.44 15 3329-3584

06 1537-1792 3.43-2.53 16 3585-3840

07 1793-2048 2.52-1.95 17 3841-4096

1.94-1.54

1.54-1.25

1.25-1.04

1. 04-. 871

.870-. 744

.743-. 642

.641-. 589

.588-. 495

24
66 One Word Sequester (KO)

See BP26. This program provides temporary storage for the counts

recorded by scaler 3.

67 One Word Sequester (KO)

See BP 26. This program provides temporary storage for the

counts recorded by scaler 4„

71* List Loader (HD)

This program reads the dials on the top board in the Control

Room. It stores this number in the object data field given by

one more than the octal number in dials 1-4. This program can

be used to load the data field of the Sequencer Program.

72* List Loader (HP)

See BP71. This program reads the dials on the top board in

Counting Room 3«

73* Sequencer (HF)

Initiating this single program allows a sequence of Board programs to be carried out. This is accomplished by loading suc- cessive words in the data field of the Sequencer Program which

have the PSB dial configuration of the desired programs. The

Sequencer program will execute successively the contents of its

data field treated as Selector Board calls until a zero word is

encountered, or the end of the data field is reached. The Sequencer program may be initiated at any place in the sequence by

setting dials 3 and 4 to one less than the desired starting

location. Some care must be taken in the use of this program,

as it carries out successive programs by modifying the Program

Selector Board interrupt program and restoring it upon leaving.

If for any reason, the Sequencer program does not go to completion, the PSB control program will be destroyed. It must be

deleted and reloaded before any calls can be made from the board.

The Sequencer program uses as its object program, the interrupt

program for the PSB. This Sequencer program has a 40 word data

field and will only operate from Selector Board position 1-4.

74* Sequencer (HK)

This program is the "20 Minute Sequencer Program" given in

Table 3. It is similar to the Sequencer (BP73) program except

that it has a 77_ word data field and operates from Selector

Board Position 4-2.

25
Table 3

00

01

02

03

04

05

06

07

10

11

12

13

14

15

16

17

20

21

22

23

24

60

61

62

63

64

65

66

67

70

71

72

73

74

20 Minute Sequencer

Group Enable 6 Off

Read Scaler Residuals - Scaler 3

Read Scaler Residuals - Scaler 4

One Word Sequester - Scaler 3

One Word Sequester - Scaler 4

One Word Sequester - P2

One Word Sequester - SEM

Scaler Save - Scaler 3

Scaler Save - Scaler 4

Scaler Save - P2

Scaler Save - SEM

Clear Scaler "Units" - Scaler 3

Clear Scaler "Units" - Scaler 4

Group Enable 6 on Load Ratio (SEM/P2 - short run)

Ratio

Load Ratio (total neutron/P2- short run)

Ratio

Load Ratio (total neutron/neutron monitor-short

run)

Ratio

Type Carriage Return-Y-Buff er

Group Enable 6 Off

Clear Scaler 2,3,4

Clear Beam Profile Data

Clear Scaler "units" - scaler

Clear Scaler "units" - scaler

Clear Scaler "units" - scaler

Clear P2 counts

Clear SEM counts

Clear TIM Data

Clear scaler Save - Scaler 3

Clear Scaler Save - Scaler 4

Clear Scaler Save -P2

Clear Scaler Save - SEM

PBS Thumbdials

57

1002 51

1003 52

51 26

52 27

1004 66

1005 67

51 46

52 47

1004 36

1005 37

1002 01

1003 01

56

40 30

40

40 31

40

40 32

40

04

57

53

1000 01

1001 01

1002 01

1003 01

1004 01

1005 01

1006 01

46 01

47 01

36 01

37 01

26
75* Sequencer (HR)

See BP74. This program is the "Final Sequencer Program,"

given in Table 4, and operates only from Selector Board Position

4-4.

76 Linkage Lister (HC)

This program gives a listing of the Interrupt and Board Linkage

tables at the time the program is initiated.

77 Loader (HA)

This is the program used to load individual machine language

programs from paper tape into the computer. The command to

load the tape is given from the typewriter and is of the form

IP0006, IPIC.

In this example, Interrupt program IPIC is being loaded into

interrupt location 06. For Board programs the I is a B. After

the period is typed, the photoreader will read the tape. When

the program has been successfully loaded, DUN will be typed.

To exit from the program, set Breakpoint 1 and type a space.

27
Table 4

Final Sequencer

00 Transfer to temporary storage - data

01 Transfer to temporary storage - beam profile

02 Read Scaler Residuals - Scaler 2 03 Read Scaler Residuals - Scaler 3 04 Read Scaler Residuals - Scaler 4

05 One Word Sequester - Scaler 3

06 One Word Sequester - Scaler 4

07 One Word Sequester - P2

10 One Word Sequester - SEM

11 Scaler Save - Scaler 3

12 Scaler Save - Scaler 4

13 Scaler Save - P2

14 Scaler Save - SEM

15 Sum Data

16 Increment Run Number

17 Accumulate Run Number 10

20 Accumulate P2 Counts

21 Accumulate SEM Counts

22 Accumulate Start Counts

23 -Accumulate Neutron Monitor Counts

24 Accumulate Total Neutron Counts

25 Accumulate Analyzer Sum

26 Type Carriage Returns-Y-Buf f er

27 Load Ratio (SEM/P2-short run)

30 Ratio

31 Load Ratio (total neutron/P2-short run)

32 Ratio

33 Load Ratio (total neutron/neutron-short run)

34 Ratio

35 Type Carriage Returns - Y-Buffer

36 Type Heading

37 Type Line of Data

40 Load Ratio (SEM/P2-sum)

41 Ratio

42 Load Ratio (total neutron/P2-sum

)

43 Ratio

44 Load Ratio (total neutron/neutron monitor-sum)

45 Ratio

46 Punch "Summed Data"

47 Clear Beam Profile

50 Clear Scaler "units" - scaler 2 51 Clear Scaler "units" - scaler 3

52 Clear Scaler "units" - scaler 4

53 Clear P2 counts

54 Clear SEM counts

55 Clear Data

PBS Thumbdials

01

01

01

01

01

01

01

1006 64

1000 61

1001 50

1002 51

1003 52

51 26

52 27

1004 66

1005 67

51 46

52 47

1004 36

1005 37

1006 25

55

55 54

36 54

37 54

50 54

47 54

46 54

25 54

04

40 30

40

31

40

32

40

04

11

02

33

40

34

40

35

40

54 05

1000 01

1001 01

1002 01

1003 01

1004 01

1005 01

1006 01

28
46 01

47 01

36 01

37 01

53

64 05

61 05

Table 4 (continued)

56 Clear Scaler Save - scaler 3

57 Clear Scaler Save - Scaler 4

60 Clear Scaler Save - P2

61 Clear Scaler Save - SEM

62 Clear Scaler 2, 3, 4

6 3 Punch TIM Data

64 Punch Beam Profile

65

66

67

70 Scope display of data 1006 60

71

72

73

74

75

76

77

«U.S. GOVERNMENT PRINTING OFFICE: 1970— 392-249/1 06

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NSRDS provides quantitive data on the physical

and chemical properties of materials, compiled from

the world's literature and critically evaluated. Product Standards. Provide requirements for sizes, types, quality and methods for testing various industrial products. These standards are developed cooperatively with interested Government and industry groups and provide the basis for common understanding of product characteristics for both buyers and sellers. Their use is voluntary.

Technical Notes. This series consists of communications and reports (covering both other agency and

NBS-sponsored work) of limited or transitory interest. Federal Information Processing Standards Publications. This series is the official publication within

the Federal Government for information on standards

adopted and promulgated under the Public Law

89-306, and Bureau of the Budget Circular A-86

entitled, Standardization of Data Elements and Codes

in Data Systems.

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further information on Clearinghouse services, write: Clearinghouse

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