A new type of photodiode + scintillator (1 m2 x 1 cm) detector is developed to detect the large electro-magnetic burst under an EX-chamber. The threshold burst size is found to be 4.3 x 10 the 5 particles at the center of the scintillator. Therefore a gamma-ray family of 10 TeV is detectable by it, when it is set under 14 r.1. of iron. In addition, a very fast (2.4 nsec width) and very bright (correspond to 10 to the 6 particles) scintillation pulse has become avarable for this study

Fukushima, Y.

Saito, T.

Sakata, M.

Shima, M.

Yamamoto, Y.

English

NASA Technical Reports Server

73 RE 4.2-6
Application of Photodiodes to the Detection of
Electromagnetic Bursts
Fukushima, Y., Saito, To., Sakata, M., Shima, M., Yamamoto. Y.
Department of Physics, Konan Univ., higashinada, Kobe, 658, Japan.
Abstract
A new type of photodiode + scintillator (i m 2 * i cm)
detector is developed to detect the large electro-magnetic burst
under a EX-chamber. The threshold burst size is found to be
4.3"10 5 particles at the center of the scintillator. Therefore
a gamma-ray family of i0 TeV is detectable by it, when it is set
under 14 r.l. of iron. In addition, a very fast (2.4 nsec
width) and very bright (correspond to 106 particles)
scintillation pulse has become avarable for this study.
i. Introduction.
Simultaneous observations of EAS and gamma-ray family have been made
by two groups (i)(2). In these observations it is important, for
successful joining of a EAS event with its corresponding gamma-ray
family, to detect the distribution of electromagnetic cascade burst in
the EAS core area. The burst distribution is detected by scintillation
counter array beneath emulsion and X-ray film (EX) chambers. In our case
(i), an unit burst detector is composed of a plastic scintillator
(50*50*3 cm 3 ) and a 2" photomultiplier tube (PMT), and the detecting
range for burst size is 103 ~ 106 particles/O.25m 2.
A new type of photodiode, recently developed, may be useful instead
of PMT for detection of such a large burst. The sensitivity of the
photodiode is not comparable to that of PMT as yet, detection of large
size burst as these observation may be possible. Photodiode have many
advantages in comparison with PMT : "low cost, miniature size and high
stability, and one can make burst detector covering large area with low
cost.
Large burst events emit scintillation light of considerable
, luminosity and _f very short duration of a few nsec. Then we, first of
all, make a pulsed light source which emits very bright pulsed
scintillation light of 2.4 nsec. It is obtained by irradiating plastic
scintillator ultraviolet laser pulse of short width less than 1 nsec.
2. Pulsed Light Source and Light Response Checker.
Short ultraviolet light of 337.1 nm is made by the method of
transverse excited nitrogen laser of Blumlein type (3). Figure 1
illustrates the cross sectional view of the laser device; the electrodes
of which have a gap of 3 mm and
N 2 Gas
%_'_3 I/ml._ _r_g_r- length of 5 cm and is operated by 14
____g____10kl2kn-_ _- 10kV kV ~ 22 kV DC high voltage. The flow
_- - of N2 gas is about 3 _/min under the
cm2 atmospheric pressure. From this
__ Epoxy laser oscillator about i0 different
spectral lines are emitted and the
20kV/ Cu-t1£m \M_rerc°rodes-ec.troaes 337.1 nm line is the most eminent in
Figure i them. In order to cut off the
visible lines we use a interference
https://ntrs.nasa.gov/search.jsp?R=19850027675 2020-03-20T17:06:38+00:00Z
74
HE 4.2-6
filter of passing only (337±15) nm. The specifications of this device
are presented in Table i. The pulse shape of the 337.1 nm is detected by
a biplaner photo tube (RII93U, Tr = 0.27 nsec, HAMAMATSU) and a
oscilloscope (7904, 500 MHz, Tektronix). In Fig. 2(a), the shape of it
is shown. Because of the limit of the oscilloscope's response the FWHM
will be smaller than 0.9 nsec which is known from Fig. 2(a). The shape
of a scintillation light made by the laser light is shown in Fig. 2(b),
from which one can observe the pulse shape of real scintillation light of
width 2.4 nsec. The stability of this laser output is less than 5% after
preliminary heating of a half hour as is seen in Fig. 3.
Spectral Output : 337.1 nm limim_"Repetition Rate 3-40 Hz
Pulse Width $i nsec _R[][][][][][]E
OutputS ability10 HilllllRD eosioo  .5"3 an[]nalaaH
(AtE. t> (ve**icsl* momimmi,mmmi
.orlzo°tal)B_m Divergence 7.7*7.7 mra_
(Half Angle) _iTrigger N2 Gas
Pr essurized Figure 2(a) Figur e 2(b)
SparkGap 0.5V/div. ,2nsec/div. 0.1V/div. ,2nsec/div.(-4 kg/cm 2)
Table i
15 * *
"
v •
§ Q • • •e e l•
, o• • • • oeO •
0 . • • eee• e• 1 Q• • • •e •
• • • oe •
-S • • °• •0 •oeoo
-", _ _ _ _ _ o
Time (x 1000_c)
Figure 3
J
The laser oscillator is put in a noise shield box and only the
pulsed light is derived through a quartz light cable. The strength of
scintillation pulse is adjusted by two functions: one is the high voltage
applied on the laser gap and the other is relative angle of polarizers as
seen in Fig. 4, which we call 'light response checker' for PMT or
photodiode. The plastic scintillator (5 mm thick), seen in Fig. 4,
converts the 100% of the 337.1 nm to scintillation light.
Figure 5 shows the response curve of PMT system which is composed of
PMT, preamplifier and mainamplifier, where output of the mainamplifier is
square wave and whose pulse width corresponds to logarithm of pulse
height from preamplifier. In addition, the "number of particles" used as
the unit of abscissa in Fig. 5 means the luminous intensity at the PMT
window; intensity of "one particle" is given when a relativistic particle
vertically traverse a scintillator of 3.5 cm thick set in a scintillator
box of our standard use (i). From this figure it is found that the
maximum luminosity generated by this light source is a few millions of
particles.
75
HE4.2-6
Quartz Light
_  15oInterference Filter
_for 337.1 n_ :_0'', scint illator _=
I00 _"
(5 mm thick) _ ."
: : Polarizers for _ .I"
_ Lumlnosity
: Control lee_
[ i _Photomultlplle r _ 50 .'"
or Photod lode • eee"
IPreamprifier Mainampr ifier
0 LOG (Particles)
Figure 4 Figure 5
3. Response of PIN Type Photodiodes.
We use PIN type photodiodes (SI723-01,HAMAMATSU) which have large
sensitive area (i0"i0 mm 2) and very high speed of response in both rise
and decay times (Tr = 15 nsec). The preamplifier circuit for this
photodiode is shown in Fig. 6, which has field effect transistor and
function of current-voltage converter. Pulse height of the preamplifier
shows a good linear relation with luminous intensity as shown in Fig. 7.
+12V
_.0, +12V ._ .Ix- I_,F T _ 0 • "
Ae
_e
S1723-04 LF357 -12V 2SC495 O_ _ LASER HV • 22 KV
" • 20KV
Figure 6 -" • leKV
-24t
LOG (Particles)
Figure 7
I00
• "j The output pulse width from the mainamplifier,
= the same type as used for PMT system, does not
.o show a linear relation with them as shown in
=.50 ,,*''" Fig. 8. From this result, however, we can
,_..*** LASER HV • 22KV conclude that this PIN photodiode-amplifier0 v system is useful for detection f local burst
_0_ i 5 _ • ISKV size higher than a few i04 particles when we
LOG (Particles) use it instead of PMT in the standard type
Figure 8 scintillator box before mentioned.
4. A Burst Detector of 1 m 2 Unit Detected by Photodiodes.
An unit pack of photodiode and preamplifier is attached to the each
corner of the scintillator whose size is 100"100"1 cm 3, and the whole
unit is wrapped with aluminum foil as shown in Fig. 9. The uniformity of
response is measured, as illustrated in Fig. i0. Numbers in the figure
show the values of relative pulse heights of the preamplifier output,
76
HE 4.2-6
where the same brightness of 337.1 nm laser pulse is directly put on each
point of the scintillator, which is well fitted by R-1.55, where R is
distance between the photodiode and each point. This R-dependence is
well interpreted by the following conditions that attenuation length is
i m, a refractive index is 1.5, and a reflective index at the boundary
is 0.97 in the scintillator.
(42) (3'0)
Tinned Sheet Iron Box
Plastic Scintillato_ 42 " B_ / • •
lO0,_,icm3 / Pasteboard
PINs lli=o.III 100
Photod lode _, /125 /325_--
,____ _Photodiode _ _m_ifi_ _ ___ i}0
Pho£od lode
Figure 9 Figure IU
The threshold burst size, detectable by the photodiode system, is
estimated as follows. First, a PMT (H.V. = -800 V) is attached to the
i m2 scintillator instead of the photodiode, and its output pulse height
was measured for real single cosmic ray traversing the position (A),
where the position (A) is shown in Fig. i0. Then this pulse height was
found to be 4.5 mV. Secondly, when a certain intensity of 337.1 nm laser
pulse is irradiated to the central position (B) as seen in Fig. i0, the
output pulse height from the PMT was found to be saturated. At lower
H.V. of PMT (-550 V), however, it was found to be 4.0 V. The ratio of
decrease of output pulse height from the H.V. = -800 V to -550 V is
0.079, which has been observed for this PMT. On the other hand, the
difference of response between the positions (A) and (B) was i000 : 83 as
seen in Fig. i0. Then the intensity of 337.1 nm laser in this
irradiation is found to correspond to scintillation light of
(4.0 V)/((0.0045 V) * 0.079 * (83 / i000)) = 1.3"105 particles of real
cosmic rays. °
When the same laser light irradiated at the same point (B) is observed by
the photodiode, the preamplifier output is found to be 24 mY. Because
the threshold voltage of this photodiode-preamplifier system is 8 mV (S/N
= 3), the threshold particle number for this system is 1.3"105 _ (8 mV /
24 mV) = 4.3"10 % particles at position (B). If this burst detector is
set beneath a EX-chamber with 14 r.l. of iron, a burst of 4.3"10 %
electrons and positron will be generated by a cosmic gamma-ray of about
i0 TeV, so that we can conclude that a gamma-ray family of EEy = I0 TeV,
at least, is detectable by this new burst detector.
References
(i) Nakatsuka, T. et al., 18-th ICRC, Bangalore, 1983, conf. Vol. 11,346.
(2) Matano, T. et al., 18-th ICRC, Bangalore, 1983, conf. Vol. ii, 342.
(3) Mitani, T. J. Appl. Phys. 52(5), May, 1981, P.3159


Application of photodiodes to the detection of electromagnetic bursts

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