A large statistics study of the performance and yields of generation-6 VLPCs (HISTE-VI) Page: 4 of 4
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Figure 6 (a) Quantum efficiency and (b)
threshold as a function of voltage. In both cases
the operating voltage is the reference.
1.E+01 1.E+02 1.E+03 1.E+04 1.E+05
Figure 7 Linearity behavior of a high-gain VLPC.
shown are the RMS, we observe that the various
chips are quite similar in these variables.
The actual behavior of the threshold as a
function of the operating voltage is exponential,
a behavior not observed in Fig. 6. This is because
our amplifier added a width to our single
pe peaks of 10-20% of the inter-peak separation,
depending on gain. Consequently, the low-
voltage threshold plateau at 0.5 pe is explained by
this amplifier width.
Fig. 7 shows the linearity behavior of a
particular VLPC pixel. This behavior is quite
typical, with only a slight dependence on gain,
operating voltage, or noise characteristics. In this
measurement, an ultraviolet laser (k=337 nm) was
used to illuminate a piece of scintillator, doped
with green wavelength shifter. The resultant light
was directed towards a small number of VLPCs.
The light was then attenuated using neutral
density filters, so that the light range varied over
five orders of magnitude (1-5x104 pe). Since we
are unable to determine whether the cause of the
5 loss of linearity is from loss of quantum
efficiency or loss of gain, we plot on the
horizontal axis equivalent photoelectrons. This is
the number of photons incident on the VLPC,
multiplied by the quantum efficiency for low
number of photons (near 80%).
The VLPCs become nonlinear by
approximately 10% at 600 equivalent
photoelectrons. This is consistent with results
published for an earlier version of the VLPCs
VLPCs have proven themselves to be a very
successful photodetector technology. They are
high rate, high gain, high quantum efficiency and
low noise devices which are well matched for use
in scintillating fiber applications.
 S. Abachi et al., FERMILAB-PUB-96-357-E.
 G.B. Turner et al., proceedings of SCIFI93,
1995; M.G. Stapelbroek and M.D. Petroff,
 M. Ambrogiani et al., IEEE Trans. Nucl. Sci.
44 (1997) 460; R. Mussa et al., Nucl.
Instrum. Meth. A 360 (1995) 13.
 D. Lincoln, Nuclear Physics B (Proc. Suppl.)
78 (1999) 281; A. Bross et al., to be
published in the proceedings of the Fifth
International Conference on Position
 A. Bross et al., Nucl. Instrum. And Meth. A,
394 (1997) 87.
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Lincoln, Don. A large statistics study of the performance and yields of generation-6 VLPCs (HISTE-VI), article, June 23, 2000; Batavia, Illinois. (digital.library.unt.edu/ark:/67531/metadc712024/m1/4/: accessed October 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.