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data acquisition, the amplified pulses from the PM tube were counted for a specific length of
time
(0.9
s), and the resulting total was stored and displayed. A histogram was then
constructed showing the count rate of the tube over the duration of the experiment
15 min).
(U)
Because the voltage output of a photomultiplier tube
is directly proportional to the
intensity of the incident light source, we decided to set two “windows” on the PM tube signal.
One window displayed the entire voltage-range output, which
is dominated by numerous,
small-amplitude background pulses. We designated this window Region
I.
The window for
Region
II was adjusted to show only large-voltage pulses.
In this fashion, we were able to
monitor the system for either of two possible outcomes:
•
A significant increase in the number of small amplitude pulses.
•
An increase in the frequency of relatively rare, large-amplitude events.
The Chinese claim that an individual with “exceptional vision” produces an anomalous signal
from the PM tube that primarily consists of large-amplitude pulses. 2
(U)
Because the PM tube was in total darkness and no light-emitting materials were
included m the sample chamber,
all background counts were caused by thermionic emission at
the photocathode or dynodes. A photon striking the photocathode will produce a signal that
is indistinguishable from those resulting from thermionic emission.
Therefore, we could not
say conclusively in our experiment whether a
statistically significant increase in count rate
(above background)
is caused by enhanced thermionic emission or by photon production.
For simplicity in this report, we have referred to the putative effect as “photon production,”
and have calculated our results assuming that photons are striking the photocathode in the PM
tube.
(U) A multichannel analyzer (MCA) with four inputs received, sorted and stored the
signals coming from the two windows. A third input was connected to a signal generator,
which could be triggered by a microswitch in the adjoining RV room.
(The fourth input was a
spare.)
The microswitch was used to mark the beginning and end of data taking in the RV
session.
(Details of the sessions are contained in the methodology section.) A schematic of
the equipment used
is shown in Figure
1.
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TUBE HOUSING
UNCLASSIFIED
RGURE
IU>
SCHEMATIC DIAGRAM
F° R THE PHOTON-PRODUCTiON EQUiPMENT
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Following an experimental session, the data collected by the MCA was transferred
to cassette tape.
The cassette was subsequently read into a computer for analysis
(see
Photomultiplier-Tube Analysis, Section D below).
The count rates during control periods in
our two regions of interest were approximately 300
s-1 and 10
s-1
respectively.
Because a
single photon can produce a count, we were sensitive to an increase of approximately
photons, where N
is the count rate.
This figure would correspond to about 50 to 60 excess
counts in Region
I, and as few as 3 to 4 excess counts in Region
II.
(U)
We exercised considerable care in reducing the sources of experimental artifact.
The PM-tube housing and slide holder were light-tight and constructed of metal, which was
grounded and shielded against
rf, magnetic, and electrostatic
fields.
In at least one Chinese
report, the
light proofing of the PM tube was accomplished by using only layers of black
cloth.
Our entire PM-tube housing was further enclosed in a standard, photographer’s film-
changing bag so that slide selection and insertion could be accomplished in the dark.
(U)
We found
it necessary to isolate and
filter the 110-V ac power to the experimental
setup.
Line transients produced by nearby heavy machinery caused spurious peaks to appear
in the PM-tube output until suitable
filters and surge suppressors were installed.
(U)
In summary, our overall method of approach was to construct the most rigorous
replication of the Chinese reports possible using off-the-shelf, state-of-the-art hardware.
Should an extraordinary effect be observed, we could upgrade various elements of the system
to include more specialized or specially selected hardware.
B.
(U)
Methodology
(U) A detailed outline of a typical RV session monitored by the PM-tube hardware
is
contained in the appendix.
Our goal was to conceptually reproduce the procedure carried out
by the Chinese while using techniques with which we were familiar, and which were consistent
with rigorous work.
For example, we did not allow the subject in the RV session to touch the
photomultiplier-tube housing.
In at least one of the Chinese papers, the authors specifically
state that the subject “must touch the cloth” covering the PM tube.2
(U)
The slides serving as targets during the session were prepared from a pool of 112
National Geographic Magazine photographs.
Each slide was placed in a separate opaque
envelope marked with an identification number.
Prior to each session, four slides were
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selected from the target pool by a random number generator.
All four slide envelopes were
placed in the changing bag with the PM-tube housing, then shuffled.
One envelope was
selected; the slide was removed and placed into the special holder that covers the PM tube.
This procedure ensured that the slide selected was unknown to the viewer and the
experimenter.
(U)
The photomultiplier tube and
its preamplifier were both positioned in the same
room used for the RV session.
Connecting cables for signals, high voltage, and the like, were
run through a
utility access space into an adjoining room where the instrumentation for
amplifying and counting the PM-tube signals was located.
The viewer and the experimenter
always accompanied each other when
it was necessary to enter the instrumentation room
during the course of a session.
At
all other times that room was locked.
(U)
Prior to the arrival of a viewer, the experimenter selected the four slides, checked
the equipment for proper functioning, shuffled the envelopes, then loaded the target slide.
To
achieve a relatively constant background-pulse rate, we always cooled the exterior of the PM
housing and changing bag with a plastic bag of ice.
(U)
This moderate form of cooling was necessary because the RV session room would
get quite warm during afternoon sessions. A rise in temperature to about 26° C was sufficient
to increase the background-count rate a factor of two or three over that observed in the
morning session.
Cooling with ice allowed us to maintain the temperature of the PM tube
near 20° C for
all sessions.
With a more elaborate housing,
it
is possible to exactly stabilize
the temperature of the tube and, hence,
its dark noise.
The additional expense and
inconvenience did not seem justified, however,
for three reasons:
(1)
The Chinese experimenters’ report changes from background rates on the
order of 102 to 103
. We would surely observe these effects even with a
background drift of a factor of two.
(2)
Our data analysis was always based on two minutes of control run recorded
immediately prior to the
first RV response.
(3)
The variable temperature housing contains a double-quartz window and
additional flanges to
facilitate rapid sample changing.
These additions
would have increased the sample-to-PM-tube distance from
1 cm to 6.7
cm, and would have caused a significant deviation from the PRC
methodology.
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After the arrival of the viewer, three minutes of data were collected with no one in
the RV room.
(The
first minute was always discarded in subsequent analysis because of
transients occurring when voltage was again applied to the PM tube after installing a slide.)
The viewer and experimenter then entered the RV room and performed an RV session
following procedures developed in other sections of the SRI program.4
Each time the viewer
was ready to give a response in the RV session, the experimenter marked that time with a
press of a microswitch.
Closing the switch briefly sent a series of TTL logic pulses, which
were registered in the MCA memory.
After the response, the experimenter again closed the
switch for
1 to 2
s.
These two bursts of pulses clearly defined the period of psychic effort for
future analysis of the PM-tube output.
Following the session, the viewer and experimenter
once again returned to the instrumentation room where the accumulated data were read out
onto a cassette tape.
Once this process began, the pair returned to the RV room, where the
target slide was removed from
its holder and displayed to the viewer.
(U)
Following the departure of the viewer, the experimenter rechecked the apparatus
and
left
it ready for the next session.
Following the manufacturer’s recommendations,
all
primary hardware (PM tube, amplifier, MCA,
etc.) remained turned on.
The data tape
remained in place until
filled (~15 sessions), and was then removed for further analysis.
C.
(U)
Hardware (Details of Construction)
(U)
In nearly
all cases, we purchased state-of-the-art, off-the-shelf instrumentation.
Where required, special-purpose items were fabricated at SRI.
Specific details follow:
•
Photomultiplier Tube—Thorn/EMI low-background, high-performance PM
tube, Model 9829 QB; peak spectral response at 400 nm with 28 percent
quantum efficiency.
The tube
is sensitive from 200 nm
(ultraviolet) to 600
nm (red light). A sample spectrum
is shown in Figure 2.
•
Photomultiplier-Tube Housing—Pacific Instruments Model 3262 RF;
nickel-plated steel with electrostatic magnetic and rf shielding.
This housing
was designed for ambient temperature use.
•
Photomultiplier-Tube Preamplifier—Canberra Model 2005, charge-
sensitive preamplifier; conversion gain of 22.7 mV/pC, noise <
1 X
10- 15 C,
15 ns rise time.
The drift
is less than ± 0.01%/°C, and the linearity
is
better than ± 0.02% of ± 10-V output.
UNCLASSIFIED
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