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- String 4: 26 OMs, all Hamamatsu, all equipped with nylon balls, all facing down except
OM#1, 10, 19, 20, 21, 23 and 25. LED modules above OM#1 and 10. Anticipating a
change of technology in the next stage of AMANDA-B and in order to perform tests on
them, twisted-pair cables from Ericsson Cable were incorporated in a separate cable instead
of coax for OM#21-26.
In addition, thermistors and pressure sensors were placed near the top, middle and bottom module
of each string to monitor it during deployment.
The most important piece of calibration instrumentation are the two optical fibers going from
the surface where they are coupled to a dye laser, to a nylon diffuser attached on the main cable
50 cm below each OM. One of them is single mode, with a FWHM time ¥ resolution of ¥ 7 ns
at 530 nm and is used for time-calibration whereas the other is multi-mode with a FWHM time
resolution of 15 ns at the same wavelength. The multi-mode fiber can transmit wavelengths
¥
of 450 nm and longer and is used for inter-string data collection mainly.
Time-calibration of the PMs is performed by pulsing a laser connected to these fibers at the
surface and, knowing the time at which the pulse reached the nylon ball, the time it takes for the
PM signal to reach the surface can easily be found. That time is the sum of the PM’s transit time
and of the travel-time through the cable of the electrical pulse it sent out. A dye-laser was used
in 1996 to take such calibration data at a 10 Hz rate.
These measurements were performed on each OM individually, at their ¢¡ § -gain voltage, so
the requirement on the light output for that purpose was not very high. However, the maximum
intensity that can be sent out at the diffusers is ¢¡ ¦ photons/pulse, which makes it possible to reach
neighboring strings. This was used to acquire data used in ice analysis and position calibration.
The laser which was installed at a depth of 1830 m on string 1 contains a -laser, built at
¢¡
UCB [35]. It has a maximum intensity of photons/pulse, which makes it easily detectable
by OMs more than 200 m away. The laser emits light isotropically at a single wavelength of
337 nm in a §
sr up-looking solid angle. It is pulsed at a 6 Hz rate, with a time resolution of
ns. ¥ The ¥
¥¦ ¢¡
Three halogen DC-lamps were also deployed, one broadband with a maximum intensity of
photons/second and two with a maximum intensity of ¡ photons/second equipped with filters
at 350 nm and 380 nm respectively. The main purpose of these light sources was to measure the
relative photon flux as a function of distance from the source.
The several LED beacons installed on strings 1, 2 and 4 can either be pulsed at 500 Hz with
a maximum intensity of ¡ £ photons/pulse or used in DC mode with ¢¡ £ photons/sec. They emit
light with a wavelength 380 nm and 450 nm.
A second harmonic generator (SHG) was also installed, which can send pulses of light at 532
nm wavelength (doubling the frequency of 1064 nm light sent down the fiber from the surface)
with a time resolution of 7 ns and an intensity of ¢¡ photons/pulse.
Six more strings were added during the 96/97 season, which make up the AMANDA-B10
detector, together with AMANDA-B4. The cables composing these added strings were of a different
construction than the first four, using twisted-pair instead of coaxial cables for signal transmission
allowing for 36 OMs instead of a maximum of 20 OMs per string.
¢¡ © fluorescence contamination is taken care of by a filter at the diffuser.
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