Radial response of the burst and transient source experiment

N90-19408 1989

NASA/ASEE

SUMMER

FACULTY

MARSHALL The

SPACE

University

Prepared

And

Response

Transient

Source

Rank:

University

and

PROGRAM

CENTER in Huntsville

of the Experiment

John

by:

A,';,demic

FLIGHT

of Alabama

Radial Burst

FELLOWSHIP

Patrick

Assistant

Professor

Mississippi

Department:

Lestrade

State

Department

University

of Physics

Astronomy

NASA/MSFC: Laboratory:

Space

Division:

Astrophysics

Branch:

High-Energy

MSFC

Astrophysics

G. J. Fishman

Colleague:

Date: Contract

Science

N(). :

July

21, 1989

The

University

Alabama

NGT-01-008-021

XVIII

of

in Huntsville

and

Radial Burst

And

Response

Transient

of the

Source

Experiment

by John Assistant

Patrick

Professor

of Physics

Mississippi Mississippi

Lestrade

State

State,

and

Astronomy

University

Mississippi,

39762

Abstract

The the

Gamma

gam:m_--ray

Ray

Observatory

universe.

Jerry

at Marshall

Space

Flight

iments,

Burst

And

the

During

my

first

includes Fishman

Center

in the

High

Source with

BATSE

team

in 1988,

correct

interpretation

energy

analysis

photopeaks

was diagnosed of the

perimeter of the events that occur In this ,,xl)lain

the

for angles

as being

large-area

ret)ort

of the

detector

due

obtained

after

data

revealed

a shift

to a radial (LAD).

10-inch radius near the disc's we analyze

non-gaussian

data

of incidence

shape

between dependence

this

radial

of the

are

not

response

photopeaks

angles.

XVIII-i

of these

exper-

in the

about

we completed

in Earth

light

events as efficiently

orbit.

centroids

70 ° and

of the

lal)o-

modules to gamma-ray are necessary for the

it is put

Energy-depositing NaI disc center.

for one

Branch

(BATSE).

measurements to test the response of the BATSE that are non-axial. The results of these observations of BATSE

to observe

Astrophysics

investigator

Experiment

the

designed

Energy

ratory sources

Subsequent

"-"

experiments

is tile principal

Transient summer

four

of the

110 °. This

collecting that

and

in so doing in the

spectra

effect

efficiency

occur

collected

seen

full-

near as

we are taken

the those

able

to

at all

Acknowledgements: The

summer

association

with

Center.

My

part

sincerely

provided

have

been

another

in the

group

at the

unselfishly

of their

time

I appreciate

all that

I have

acceptance

like to thank

His patience

chapter

Astrophysics

given

group.

for their

I would

me.

has Energy

of the

grateful

In particular has

High

colleagues

me an integral am

of 1989 the

with

and Jerry

exciting

story

of my

Marshall

Space

Flight

and

expertise

learned

to make

from

them.

I

friendship. Fishman

my naive

for the

questions

opportunities

has

been

that

he

of immeasurable

help. I am also for his help format. time

he has The

visiting

to Dr.

in converting

Several

a credit

times

administrative faculty,

friendship Ellen.

data

from this

provided aspects

Six,

Jerry

to run

I would

Edward

during

unhesitatingly

to Frank

Finally, and and

indebted

West

of the

eight-inch past

floppy

summer

Physics

diskettes

I have

Branch

of MSFC

to a PC-compatible

called

upon

him

and

each

help.

of a program

Karr,

Solar

and

Mike

this

large

are

quite

complex.

Freeman

that

it appears

show

appreciation

for

Bob,

Bob,

It is

to us,

the

so effortlessly. be remiss

of Chip,

Tom,

if I didn't John,

Scott,

also Jeff,

Philip,

Bill,

John

the

Patrick July

XVIII-ii

support

Billy

Bob,

Lestrade 21, 1989

_"

List

of Figures page

Figure

1 BATSE

detector

Figure

2 Gamma-ray

Figure

3 The

Figure

,l Peak

Figllre

5 Cs-137

module

spectra

spectrum centroid

(Cesium-137)

burster

shift

and

for Cs-137 peak

gaussian

showing

C Source

holder

Figure

7 Source

positions

for the

Figure

8 Hg-203

279 keV

peak

Figure

9 Peak keV

Figure

peak

10 Three Hg-203

Figm'c

1 l Peak keV

Figm,,

12

i"ip_;llrc 13

(72,

peak

Figure

14

Comparison photopeaks = 0.(t20,

Figur('

for modules

Fip4urc

17 Comparison spectra

tests ...........

XVIII-15

9.5 in. in TPS-119

.....

for Hg-203 XVIII-17

response

Am-241

for

(60 keV) ........... number)

XVIII-18

for Hg-203

279

response

Hg-203

XVIII-19

number) and

XVIII-16

for Hg-203

279

P ............... functions

279 keV

XVIII-20 (solid

lines)

and

peak ............

XVIII-21

of observed (solid) and calculated (dotted) for Cs-137 662 keV for the case r0 = 5.5 in., and

edge

deficiency

of observed

(solid) and

of observed 0.020,

= 10%,

662 keV

=12%,

fox Cs-137

_: = 0.015,

radial

7, 0/8,

radial

(.,tge deficiency

photopeaks

XVIII-14

4-6 ...................

for Cs-137

Comparison

XVIII-12

tests ............

number)

(channel

XVIII-11

XVIII-13

response

(channel

position

15 Comparison photopeaks

radial

and

for modules

of the

IMP-6).

1-3 ...................

position

measurements

and

inadequate

response

fits to the

theoretical

(OSO-7

Se-75 .............

the

(channel

279 keV)

centroid

event

at r = 0, 6, and

for modules

peak

Three

radial

position

centroid

Peak keV

for the

quadratic

XVIII-10

.....................

Figure

centroid

XVIII-9

...............

of a gamma-ray

full-energy

fit of a single

..................

and

for the

662 keV

and

0.025,

and

of Monte

Carlo

(dotted)

for Hg-203

case

case

6.0 in ........

.....................

XVIII-23

(dotted) r0 = 5.5 in.,

deficiency and

XVIII-22

a = 0.020,

calculated

edge

14% .......

(dotted)

5.5, and

for the

and

and

calculated

r0 = 5.0,

(solid)

12%,

observed

=12%

......

XVIII-24

(solid) XVIII-25

XVlII-iii

1.

Introduction:

1.1

The

Gamma-Ray

Before These

the

Observatory

year

2000

observatories

and

gamma-ray

earth,

the

portions

planets,

high-energy

Since

i)cculiar cv,'ry

the

and

of the

spectra

The

more

than

9 major

infrared, objects

exotic,

space

visible,

mismons.

ultraviolet,

to be studied

cosmological

x-ray,

include

objects

the

in which

place. objects

of the

frequency

of GRB's

spectrmn.

to locate

The

visual

that

first

will be studied

in 1969

of discovery

a companion

therefore

their

the

and

order

the

we have has

is the gamma recorded

reached

decays.

decay

phase.

source

of energy.

Hurley

(1989).

cn('rgy

agree

that

ray burster

hundreds

of these

approximately

this

one

platform

for the

data

study

Energetic

Source

at energies altitude The

satellite

Experiment

GRB

from

30 keV

High-Energy

(450

measured

in milliseconds

very

rise

display

short

periodicities

times

of gamma-ray

bursters

has

been

Higher

resolution

of models

which

is nearing

completion.

writing,

final

4 experiments;

GRO

and

instruments

is scheduled

Its nominal Branch XVIII-1

lifetime

space,

Ray before

Oriented

Telescope the

by

and For-

Observaits launch

Scintillation (COMPTEL),

Burst

detect

given

earth-orbiting

Gamma testing

primary

abound.

major,

the

Compton

(EGRET), these

currently

The

undergoing

Imaging

in time,

One

and

in brightness as the

Together,

Astrophysics

are

star

Experiment

km).

and

durations

show

is imminent.

to 30 GeV.

to GRB's

burst

a neutron

dozens

the

inability

adopt

carrying

(BATSE).

of 250 miles

GRB's

Attempts

This

distances

Typical

portion

being

data

(OSSE),

Gamma-Ray

Experiment

the

of this

they

needed.

in GRB

of GRB's

is a 17-ton

Spectrometer

are

to eliminate

t()ry (GRO) is, at the time in the summer of 1990. GRO

review

to assign

ray

bodies.

successful.

unknown.

models

gamma

astronomical

shortest

several GRB

excellent

imp,'ovement

the

to the

partially

difficult

In general

Further,

better

are necessary

tunately,

with

Current

An

only

remain

minutes.

longer the

been

it is also

of seconds

totally

for explosive

have

magnitudes

several

almost

strange

means

of tens

during

All

confined

is quite

absolute

longest

somewhat

are

counterparts

to locate

the

other

more

in the

spectrum.

taking

enigmatic

The

to launch

two days. The

on

sun, are

discovery

objects.

plans

the universe

of the

the

processes

One of the more (GP,[t).

NASA

will study

And

Transient

gamma

radiation

to be launched

to a nominal

is five years.

in the Space

Science

Laboratory

at Mar-

shall

Space

tors.

As

Flight

has

a NASA/ASEE

the laboratory data.

1.2

Center

Burst

Summer

testing

And

of the

complete

name

sky

implies,

short-lived.

This

The principal is a sodium

and

a thickness

observer's the

output

the

case

this

has

from

in the

in Figure

When the

sponse

on

the

in the

Compton

record

study

of the

by

the

gamma-ray

of gamma-ray

radiation

that

of

acquired

earth.

As

the

events

that

are

bursters,

it also

are long-lived

- such

crystal

tends

is, given

were

chosen

(i.e.,

to

30 keV,-_

crystal,

are

Still

In

contributions

to in the

noise,

monoenergetic

spread

which

result

strikes

into a wide in only

in one

of the

of their

photons

XVIII-2

the

and

other

input

into

peak

partial

sodium

converted

(of. 662

deposition

events

lose some

iodide

into

channels

energy

as lower-energy

other

input, nature.

fluctuations

electronic

the

Examples of the resultant output a typical gamma-ray spectrum has

completely

part

recorded

that

spectrum.

as counts only

are

statistical the

effect

instrument's

there

signal,

energy

of photons

photons

is the

a uniquely-valued

the

to spread

events

to the

science

reflecting

an electrical

is the input

deposit

continuum.

of the

as BATSE,

in the

beam

become

That such

scattering

recorded

photons

size

(Price, 1964). As seen here,

features

of the

and

in values

contributions

other

These

data.

into

Not only

becomes

detector.

blocked

and

in an observational

instrument,

2), but

some

some

analysis

in some

(Figure 1). These modules will orientation it is able to monitor

temporarily

shape

spread

a monoenergetic

that

However, the

add

detector,

in the

detec-

Calibration

energy

of these

crystal

involved

is the

inhomogeneities

complexity.

k_'V peak

been

of gamma

The

an approximate gaussian shape spectra are shown in Figure 2. additional

I have

and

BATSE

to the low-energy gamma ray spectrum measurement of very weak sources.

a finite

of gamma-ray Each

part

inherent

of a gamma-ray

sources.

Fellow

to observe d'etre

inches.

problems

contains

dispersion

the

Experiment

that

and

instrument

conversion

testing

detector in each module is called the Large-Area detector (LAD). iodide crystal in the shape of a disc with a diameter of 20 inches

Testing

of the

is now

detector modules of GRO. In this

its raison

more sensitive to permit the

BATSE One

for

and

modules

to observe sources and black holes.

of 0.5

make BATSE 240 keV) and

1.2.1

of eight "corners" is designed

Although

has been designed ms the sun, pulsars,

Faculty

Source

except

BATSE

built,

BATSE

Transient

BATSE is composed be situated at the eight the

designed,

and

an electrical of the

are

and energy

crystal

re-

photopeak.

scattered

show

in

out

of

up as counts

outside

of (often _"

behind)

the

recorded input

crystal

and

as counts

are then

in the

is monoenergetic,

way.

When

the

the

situation

backscatter these

source

scattered

sistent

more

with

trmn

that

depends

a model

based

than

monoenergetic

was

the

incident

on how

on

on the

the detector

ti(,n

of not

only

part

of our

responsibility

the

results

During detectors

responding

expected

radial

event

to the

effect

crystal

also

observed,

th(

crystal

was

137 and

Se-75

this decrease' this report -- the

The allgles

but angle

not

decrease

fully

of the

are

This

angle

c('nter.

This

and

words

that

,:()lloction m(,ves

i)rocess.

from

the

more

true

spec-

problem

that

response

is a func-

describes

At

MSFC

the

detec-

spent the past year and various conditions. This

of the shift

between

how

flux.

the

about

the

due

a shift

energy

70 ° and

to the

efficiency

that

a property As the

whole

is about of the

90 ° was

crystal

disc

at

is turned 0 ° to that XVIII-3

but

the

principal

local

area

projected

by Lestrade

beam for Cs-

full-energy

of

(1988).

secondary

angle

In

effect

of incidence. photopeaks

as being

due

for to a

detector (LAD). the detector has deposited

a property area

as

dependence

of this

for that

What

incident

angular

of the

as

decrease

total

rather,

changes

centroids

detail

diagnosed

12% less than

scintillator,

peak

of the

increasing

of the

in

smaller

in the

four

oriented

was observed.

implications with

centroids

response

energy

The

at least

are

70 ° to 90 °. This

4.

the

are

detectors

decrease

in greater

with

there

detector

observed from

in Figure

in the

these

This

was

is discussed incident

orbit

Since

changed

concerned

of the

is not

the

of incidence.

matrix

radial dependence of the light collecting efficiency of the large-area Measurements showed that for energy deposited near the perimeter, collection

certainly

determine

photons.

in earth

expected,

is shown

decrease

a light

th('

ray bursters,

a complicated

in efficiency

to the

In other

we are primarily

of incidence

when

complicated

tests.

to know

of incidence

photopeaks

discovery

also

response

relative

is complicated

apparent

we can

a response

for BATSE

is the

rotated.

d_.crea._cd as the

but

flux of radiation.

is turned

was

becom("

even

of gamma

These

To this end we have several sources under

diffhrent directions, it is important a flmction of th(" angle of incidence. The

figure,

they

TPS-119

a gamma-ray

ar(:_t as the

where

in a very

case

solve

to incident

energy

report

Before

we must

is to provide

Response:

in this

spectrum

bremstrahlung.

responds

of the

crystal

of a gamma-ray burster (Metzger et. aI., 1974). spectrum is typical of these events and is concase.

-m input spectrum. the spectra with

Radial

the

as in the

thermal

tor's eff¢'cts on a half measuring presents

the

complicated.

detector,

incident

into

As seen

distort

is not monoenergetic,

is considerably

complicated

2.

peak.

effects

Figure 3 presents an observation exponentially decaying energy

The

back

of energy perimeter

near of the

the light-

deposition facing

the

sourceat 90° .

Therefore, of many

a superposition to the

left

(i.e.,

lower

At angles of the

disc.

near

The

0 ° the

former

localized

is seen

region

that

show

of the

5. This

at 266 °, on the a purer

crystal

(cf. Lestrade,

the

annulus

between

2rrdrewhere

a is a constant

radial

response.

yet

The

integration

total

peak

in this

figure

has

hand,

the

peak

because

might

expect, This

Measurement

and

Na-22

nine

modules

below

annuli

sources (eight

reasons

flight the

from

is

662 keV a centroid

at a lower they

peak

of

is a superposition

arise

at 662

energy, from

are

a more

the

used

r + dr of the

and

LAD

is the

simple

Eo (r)) 2,

(

the

center

spectrum task.

- we would

centroid

position

per channel

to perimeter,

E0(r)

is the

is therefore

given

viz.

(2)

P(E),

to be able

to solve

We decided

to approach

the

problem

The

Am-241

directly

1)

measure

Equa-

E0(r).

Response

radioactive on only

of the individual gaussians radius, r. In this case, the

2_rre-a(E-E°(r))_dr.

1°

an easy

Radial

modules

disc

a measured

way

were

_ ( E-

P(E),

=

is not

lists

and

and

of the

table

r

in counts

given

straight-forward

the centroids of only the

to be determined,

of these

(2) for E0(r).

hi.qtorical

the

photopeak,

P(E)

The

photopeak

Integration

contribution from gaussian given by

2.1

all areas

1988).

If we assume azimuthal symmetry, then constitute the photopeak are functions

tion

from

270 °) the

presents

shape

that

in a more

90 ° (or

figure

other

gaussian

Disc

One

contributions

incidence

shown

2.1

by the

near

at normal

gaussian

taken

and

shows

of incidence

in Figure

theoretical

spectra

l¢.ss dispersed,

photopeak

perimeter.

of 0 °. Note

The

Similar

the

effect

at an angle

resultant

for angles

of only

of gaussians. keV.

energies).

However,

representative

Cs-137

when the crystal is illuminated at any angle, the output is gaussians, not centered about the true centroid, but shaded

sources

detector

one protoflight). are numbered XVIII-4

DM

used

in this

1. Mercury-203

For the 1-7, 0/8,

purposes and

test. was

of this

used report

for all and

'P'. ---

Radioactive

Sources

Isotope

Energies

241A._. g5 ....

458 yr.

59.5

90

203 Hg

Sodium-22 indicates

a source the

positions wc were across

gamma-ray

of the

and

of the

regions

shift

2) the

of the

built

The

1275 indicate

for this

test,

(Figure

6).

disc

illuminated

spot

By illuminating

in peak width

centroid

of the

and

279.2

brackets

of the

chosen.

instrument

all portions

square

0.75 inches.

1) the

511,

especially

to local 7 were

crystal

response fronl

not

gaussians

Fifteen

size on

contaminated

radial

was

were

by the

able

the

a small

holder

that

peaks.

we were

such

as the

sum

dis(:

region moved

a result

of

combination

disc.

Results

Figure

8 presents

increasing

radial

(,1,t as 6 inches Figure of radius the

left

the

radial

may

have

th,"

same

Further other

right

the

and

of the

disc

the

measurements.

For completeness

With alL_l the int,:resting

an idea radial

to simplify

the

Eo(r)

functional

are three

singular

At

first

from

the

photopeaks performing of the XVIII-5

depression

when

Its presence

this

10 shows,

DM left

in

that

as Figure

formulae

from

1 is used.

in the

center

will not affect

for the

energy

of the

peaks.

of these

and form

data

the

centroid

positions

vs. ra-

6 modules.

gaussians

centroids

the

we thought

of tin purposely the

as far

is significant. 3 as a function

the

nuclides

with

for points

1 through

sensor.

centroid

shift

Note

12 present

remaining

the

figures,

of all light

Figure

centroid

However,

piece

figure

in peak

response

center.

spectra

for these

of the

of the

to reconstruct

for o_ and

disc

- a small

11 and

for the

of the width

dependence

to try

by substituting

the

in this

in radius

peak

averaged.)

of an unneeded

Figure

279 keV

radial

in the

Included

as a quadratic

for modules

in measurement.

culprit

a ft_:r removal

in the

shift

at 9.5 inches

positions

1 near

is evident

shift

following are

by an error

found

the

However,

centroid

for DM

to show

is minimal

center.

(In this

caused

deficiency

for the

disc

sides

response been

spectra

There

the

9 presents

and

Hg-203

position. from

checking

centroid

three

for Hg-203.

of this module

order

flux

in Figure

to measure

the face

the electronic

dbls

collimator

to be approximately

hoping

of gaussians 2.2

and

gammas,

(MeV)*

[72.9],

2.62 yr.

coincident

holder

as shown

was calculated

47 d.

22 11Na

* underscore

Response

Half-Life

Mercury-203

to restrict

in Radial

ASymbol

Americium-241

With

Used

the localized peaks,

measured the radial

of the

disc

it would

in full-disc

illumination

integration response,

regions

we thought

in equation E0(r),

be

(2).

In

we assumed

a

constant centroid position for gaussiansformed within a distance r0 and

a linear

with

the

decrease

from

measurements

that

of the

point

to the

279 keV

peak

perimeter.

Three

are shown

such

in Figure

radial

response

function

Eo(r)

"=

in this

{ f°o-r(1 -f)-fro) (10-to)

where

£0 is independent

of r and

result

from

r < r0 and

events

where

in centroid position for gaussians figure 12 f = 0.12 and r0 = 5 in. With

P(E)

=

this

jr0 r°

Performing

function,

equation

27rrc-_(E-£°)2dr

the

first

7rr_e -_(E-g°)2

case

+

integration

+

equals f

is given

£0 the

is the

(2) reduces

to

_rl 0

going

on near

(3)

0_