Registration and identification of muons and muon groups penetrating into the ocean depth, can be performed using a modular multilayer detector with high resolution bidimensional readout - deep underwater calorimeter (project NADIR). Laboratory testing of a prototype sensor cell with liquid scintillator in light-tight casing, testifies to the practicability of the full-scale experiment within reasonable expences

Demianov, A. I.

Sarycheva, L. I.

Sinyov, N. B.

Varadanyan, I. N.

Yershov, A. A.

English

NASA Technical Reports Server

206 HE 5.4-15
MODULAR DETECTOR FOR DEEP UNDERWATER REGISTRATION
OF MUONS AND MUON GROUPS
A.I.Demianov, L.I.Sarycheva, N.B.Sinyov, l.H.¥ardanyan,
A.A.Yershov
Institute of Nuclear Physics, Moscow State University,
Moscow II9899, USSR
Abstract. Registration and identification of muons and muon
groups penetrating into the ocean depth, can be performed
using a modular multilayer detector with high resolution
bidimensional readout - deep underwater calorimeter (project
NADIR). Laboratory testing of a prototype sensor cell with
liquid scintillator in light-tight casing, testifies to the
practicability of the full-scale experiment within reason-
able expences.
Introduction
The most popular conception of DUMAND, in its optical
version, is a spatial latticQ with numerous PMTs in sites,
serving as immediate receptors of Cherenkov radiation, pro-
duced by high energy particles in the sea water. On the ex-
perimental plane, any practical approach to such a design
makes one ponder upon many an implicit circumstances, e.g.
persumably unsteady operational conditions du_ing a long-
running period.
The intricate combination of natural factors - as deep-
sea currents, plankton migrations, bioluminiscence, etc. -
would very likely result in sporadic variations of water
transparency, light background, and other substantial para-
meters. Besides, unsufficient rigidity of the whole immen-
se construction does not exclude some accidental and in-
tractable changes in the preset sensor geometry or inter-
orientation. All these problematic issues should not be ig-
noted as a source of possible ambiguity in data interpre-
tation.
Modular Underwater Calorimeter
We have proposed /I/ a more compact apparatus, in which
the sensor cells have closea sensitive volume and hence
their parameters unaffected by the minute changes in outer
medium. In the structural respect, these cells are metal
tubes 30-50 cm in diameter and I5 m long, filled with li-
quid scintillator and viewed from both butt-ends by two
groups of P_Ts. The tubes are assembled in planes I5xI5 m2
fixed on rigid support frames; 6 such planes spaced 2m apart _
one above another with alternating tube orientation, form a
calorimeter module, which contains I80-300 sensor cells with
independent analogue readout.
The operation of electronics - data acquisition, proces-
sing and transient recording, autotrimming and system test-
ing - are monitored by a local computer, which is housed in
a sealed case close by the sensor array and communicates
with the central control station on shore via a low-speed
cable line.
https://ntrs.nasa.gov/search.jsp?R=19850027812 2020-03-20T17:10:58+00:00Z
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IO7
The fiducial volume of such a module is 2.I03 m3 o_ wa-
ter, angular track resolution 30-50 mrad, energy resolution
for electromagnetic bremsstrahlung showers 5-6%. A full-
scale experiment should include some IO0 modules, placed
firm side by side on the bottom at 3 km below the ocean sur-
face (project NADIR).
As a stand-alone experimental installation, it will al-
low investigation of the features of high-energy muon flux
and associated characteristics of primary cosmic rays and
nuclear-cascade process in Earth's atmosphere. In particu-
lar, single muon spectrum can bemeasured up to IO0 TeV,
while the data on muon groups must yield information about
the chemical composition of cosmic ray radiation at ener-
gies of primary nuclei _ IO TeV/nucleon /2/.
Prot,,otypeScintillation Sensor
At this stage, we have buiit and tested in laboratory
a prototype sensor cell for the deep underwater calorimeter,
its architecture and functions being the same as those of
the practical one, excepts for size.
Fig. I presents a sketch of the cell construction.
A light-tight casing (I) poured with liquid scintillator
(whitespirit) is manufactured of thin-wall alluminium tube
I5 cm, closed from hurt-ends with plexiglass windows (2).
Electronic equipment (3) is sealed in two identical allumi"
nium containers (@) rated at high external pressure and at-
tachable to the flanges at the opposite ends of the tube.
When immersed in the water, the excess of the tube buoyan-
cy-originating from lower density of whitespi_it relative
to water - is expected to compensate the effective weight
of massive containers.
From each container, 3 P_Ts (5) view the scintillator
through a conic 5 cm thick plexiglass illuminator (6) glued
into an alluminium hoop, which is adjusted to the container
mouth and equipped with rubber packing rings for hermetiza-
tion.
A double-conductor waterproof cable (7) connects the
containers with each other, and with minicomputer "Electro-
nica-60" serving for an "executive controller" monitored
from a remote terminal. The intercommunication is carried
. I
,j t
Fig. I
208 HE 5.4-15
out at a frequency 20 kc (IO4 bit/sec transmission rate).
The same cable is used to supply power voltage +I2 V feed-
ing the electronic equipment.
Elect tonics
The basic elements of the front-end control/data acqui-
sition electronics are diagrammed in fig.2. It is subdivi-
ded in two twin modules, each occupying one of the two con-
tainers.
The general purpose elements available in both modules
are: a power supply block (I) transforming +I2 V from the
supply main into stabilized +9 V, _5 V and-I0 V DC; a mo-d le controller (2), an interface ) performing data and
command exchange between the modules and with the "executi-
ve controller"; a first-level ma_0rity coincidence circuit
(_) firing on coincidences of at least 2 (any) of 3 PMTs!
and a LED driver (5) intended for calibration of PMTs on
the opposite end of the sensor cell.
Three identical PMT channels include8 high-voltage con-
rotters for PMT feeding (6) with 8-bit output.potential, set-ring by means of a computer-monitored DAC (7), I2 bit PMT
noise counters (8); pulse shapers (9)_ aad. 7-bit log ADCs
for pulse-height digitization (IO).
commun_a_, highway brar_h
"AGTIVE_" "PASSIVE,"
Fig. 2.
209
HE 5.4-15
In addition, one of the modules contains a second-level
(intermodular) coincidence circuit (II), and a "mask regis-
ter" (I2) fitting an actual pattern of trigger bits to the
computer-defined trigger-enable mask. This module (named
"active") initiates a regular intercommu_cation cycle, ad-dressing its counterpart (named "passive ) and the "execu-
tive controller" on detecting of an "event" or routinely
once every I0 sec on receipt of a timer signal.
Laboratory Test Data
The emphasis of the laboratory tesbing programme was
focused on the following subjects:
Technological solutions conditioned by the specificity
of sensor cell operation deep in the sea water;
Realistic parameters and optimum operational rates;
Stability and reliability of electronic equipment; and
Actual money and labour consumption, in view of the pro-
spects for serial production of like sensor cells for the
full-scale er_eriment.
The general conclusions are that rather not elaborate a
device, as that described in the preceeding sections, may be
running for a long period of time without logic malfunctions
and significant drift of parameters. Of particular importance
for this type of detector is the efficiency of light collec-
tion onto I_T's photocathode from a relatively short and
distant particle track, since the optical contact between
the liquid scintillator and metal cistern eliminates total
internal reflection. The laboratory test data indicate that
due to high transparency of whitespirit (attenuation length
estimated to exceed I0 m), the reliable registration can be
anticipated of a minimum ionizing particle traversing some-
" where a ISm long sensor cell, with sufficient pulse-height
resolution, unless the inner surface of alluminium casing
is too much tarnished (reflection coefficient below 0.6) -
. a restriction that would hardly cause any technological
problem.
On the whole, judging from the experience obtained with
the prototype sensor cell, the full-scale experiment seems
to be realizable within reasonable expences.
" References
I. G.L.Bashindzhagyan etal. Deep Underwater Measurements
with Ionization Calorometer. - I7th ICRC, v.7, p.I_I-I_+
" (Paris, I98I).
2. I.N.Vardanyan et al. Experiment "NADIR": Single Muon
Spectra and Muon Groups in the Ocean Depth. - All-Union
Cosmic Ray Conf. (Yakutsk, I98_) - in Russian.


Modular detector for deep underwater registration of muons and muon groups

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