.org. This paper was presented at the
10th International Conference on Cold Fusion. It may be different from the version published by World
Scientific, Inc (2003) in the official Proceedings of the conference.


Strong Enhancement of DD-reaction Accompanied by X-ray
Generation in a Pulsed Low Voltage High-Current Deuterium
Glow Discharge with a Ti-Cathode

A.G. Lipson
1
, A.S. Roussetski
2
, A.B. Karabut
3
and G.H. Miley
1

1
University of Illinois at Urbana-Champaign, Dept. Nuclear, Plasma & Radiological Engineering, Urbana,
IL, 61801 USA
2
P.N. Lebedev Physics Institute, The Russian Academy of Sciences, Moscow 117924, Russia
3
State Scientific-Industrial Association Luch, Podolsk, Moscow Region, 142100, Russia

Using noiseless solid state plastic track (CR-39) and Al
2
O
3
:C thermo-luminescent (TLD)
detectors, the yields of 3.0 MeV protons (from DD-reaction) and soft X-ray photons emitted from the
cathode are studied in the pulsing-periodic deuterium glow discharge with Ti-cathode at low
discharge voltages (ranging of 0.8-2.5 kV) and high current density (300 600 mA/cm
2
). Analysis of
DD-proton yield versus accelerating voltages, allowed to estimate the deuteron screening potential
value U
S
at the deuteron energy range of 0.8 < E
d
< 2.45 keV. It was found a strong DD-reaction
enhancement in glow discharge (the effective screening potential U
e
= 610 ±150 eV) compared to that
for accelerator experiments at higher deuteron energies (E
lab

2.5 keV) and lower beam current
density (50- 500
µA/cm2). X-ray measurements showed an intensive (I
x
= 10
13
-10
14
s
-1
-cm
-2
) soft X-ray
emission (with a mean energy of quantum E
x
= 1.2-1.5 keV) directly from the Ti cathode. The X-ray
yield is strongly dependent on a deuterium diffusivity in the near the surface layer of cathode.

1. Introduction

Recently performed accelerator experiments at relatively low projectile energies (E
pr
)
lab
5.0 keV
[1-9] show presence of non-negligible screening effects in the majority of metallic targets, in particular
under the deuteron bombardment. It should be noted that experimental study of fusion reactions in metal
targets for light nuclei indicates exponential gross of the reaction enhancement (or astrophysical factor S)
with projectile energy decrease. Even for gaseous D2 target bombarded with low energy deuterons down to
(E
d
)lab = 3.0 keV, the deduced screening potential U
e
=25
± 5 eV was found to be remarkably higher than
adiabatic limit of DD-reaction in Deuterium molecule (U
ad
. = 14.0 eV) [1].
For the most metals and some metal oxides [6-9] the experimental DD-reaction enhancement and
deduced screening potential U
e
are rather larger than those measured for gaseous targets and predicted from
the standard approximation of DD-reaction cross-section to low energies [10]. So, in [8] during the PdO-
target bombardment with low energy deuterons down to E
lab
=2.5 keV the experimental yield of D(d,p)T
reaction corresponding to the screening potential U
e
=600 eV, was found to be 50 times higher than that
predicted from the standard DD-reaction cross-section deduced from the Bosch & Halle approximation for
DD-reaction yield to deuteron energy E
d
= 2.5 keV [10]. In the works of F. Raiola with co-authors [6,7] the
yields of D(d,p)T reaction and screening potentials deduced from astrophysical factor were studied
systematically for about 30 simple elements of Periodic table, including both metals and some non-metal
elements. It was found that majority of studied metals posses a large screening potential U
e
> 100 eV,
excluding, mainly, metals of group 4 (Ti, Zr, Hf) and group 11 (Cu, Ag, Au). The authors [6,7] did not find
any specific experimental conditions and properties of bombarded targets (including accelerator deuteron
current density, crystal and electron structure of metals, Z number, as well as deuterium diffusivity in the
target) affected the DD-reaction enhancement and screening potential gain. At the same time it should be noted that accelerator used in [6,7] allow achieve a weak deuteron beam current, ranging from 1-54
µA and
therefore, to measure deuteron yield only at relatively high deuteron energy (E
lab
> 5.0 keV).
J. Kasagi et al. [8,9] operating with higher current low energy accelerator (D
+
beam current
ranging 60-400
µA) recently measured D(d,p)T yields in several metal and metal oxide targets down to E
d

= 2.5 keV and found that screening potential value U
e
at such beam intensity is strongly effected by
diffusivity of deuterium in metals. In the case of metals possessing a low deuterium diffusivity and a high
activation energy of deuteron diffusion (Ti and Au) the screening potentials were found to be low: 65
±15
eV and 70
±10 eV, respectively. These screening potentials only two times above that for D
2
gaseous
targets. Contrary, for Pd and PdO targets with high deuterium diffusivity, the U
e
= 310 and 600 eV,
respectively [9], appeared to be high enough to be referred to gaseous like valence electron screening.
So far, the DD-reaction yields in metal targets were studied using only accelerators with relatively
low beam currents (J
d
400 µA) and deuteron energies E
d

2.5 keV. Further decrease in accelerating
voltage leads to unwilling problems of the beam current supporting, that makes it impossible to detect DD-
reaction products within reasonable experimental time, due to their vanishingly small yield. At the same
time, the study of DD-reaction yield/cross-section behavior at lower deuteron energies (below the 1.0 keV
range) is of a great interest in terms of astrophysical and thermonuclear processes.
Meanwhile, the alternative opportunity exists to study DD-reaction yield for even Ed
1.0 keV
projectile deuteron energy range using high-current pulsed Glow Discharge in Deuterium. Earlier, it was
shown [11] that the glow discharge of such a type is enable to generate deuterons with energy and current
density ranging from 0.8-2.5 keV and 300-600 mA/cm2, respectively at the discharge deuterium pressure
ranging from 2-10 mm Hg. The current density achieved on a Glow discharge deuteron bombardment of
the cathode is about 3 orders of magnitude above that for the best low energy accelerators. The preliminary
estimation shows that a high current GD deuteron bombardment of the cathode-target could allow detection
of the reaction products down to E
d

1.0 keV (for about several tens hours of GD operation), assuming the
exponential enhancement of DD-reaction at lower deuteron energy. Moreover, the high-current glow
discharge cathode-target bombardment may induce a measurable level of X-ray emission that was predicted
for DD-reaction in the lattice environment [12] and detect it, using simple X-ray detection facility.
In present letter we show results of systematic study of DD-reaction and X-ray emission yields
during very low energy deuteron bombardment (in the energy range 0.8 < E
d
< 2.45 keV) of titanium
cathode in the high-current pulsed glow discharge. The results of thick target yield measurement with Ti-
cathode allowed to obtain unusually high DD-reaction enhancement (about 9 orders of magnitude larger
compared to the standard Bosch& Halle approximation of DD-reaction cross-section to lower energies) at
very low deuteron energies, described by the screening potential U
e
=610
± 150 eV.

2. Experimental technique

Detection of charged particles from DD-reaction and X-rays was carried out in-situ in glow
discharge vacuum chamber during discharge operation at different voltages and currents. The principal
diagram of glow discharge facility with appropriate detectors shown in Fig. 1a,b The distance between the
moving massive Mo anode and removable cathode ( thickness h = 0.01 cm, area S = 0.64 cm
2
) was varied
within 4.0- 5.0 mm. During the discharge operation the glow was spread for all cathode area, so discharge
regime used can be considered as anomalous one [13,14]. The current and voltage repetitive pulses have
a square - like shape, duration
200-400 µs, pulse repetition frequency of 5 kHz and a short arise time
(less than 1.0
µs). The pulse parameters were continuously monitored upon the discharge operation by 2
channel (divided by U and I channels ) 100 MHz memory oscilloscope. The power supply used allow to
obtain a stable glow discharge regime in the range of deuterium (hydrogen) pressure P = 2.0 - 9.0 mm Hg.
During the discharge operation the high current (voltage) fast pulsation has not been typically observed
within 10 ns time resolution. It was found that the strict continuous deuterium pressure stabilization during
discharge operation is resulted in stabilization of discharge voltage and current. At the conditions of the
quasi-stable glow discharge the D
+
energy in laboratory system would be exactly equal to voltage applied
because the very low ionization degree in those type of glow discharge ( i
< 10
5
), allow rule out
completely the deuterium plasma maxwellization [13]. At those established glow discharge regime, the
uncertainty of the mean deuteron energy was found to be
± 10 % of their nominal voltage and is mainly
determined by residual small instabilities of discharge voltage/current. Measurement of volt-ampere characteristics of the discharge at constant deuterium pressures
shows a good proportionality between the discharge current and voltages in the ranges 100-300 mA and
800-2000 V, respectively (Fig.2). In order to obtain maximal measurable. DD-reaction yield, the maximal
currents were chosen at appropriate deuterium pressure to comply with the deuteron voltages employed, in