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Progresses on understanding LENR-AHE effects, using thin and long Constantan wires multi-elements coated, under D2 gas mixtures at high temperatures, by DC/AC Voltage stimulation in coiled coaxial geometry.

Francesco Celani(1,2), C. Lorenzetti(1), G. Vassallo(1, 3), E. Purchi(1), S. Fiorilla(1), S. Cupellini(1),

M. Nakamura(1), P. Cerreoni(1), P. Boccanera(1), R. Burri(4), A. Spallone(1,2).

1) ISCMNS_L1, Via Cavour 26, 03013 Ferentino-IT; 2) INFN-LNF; Via E. Fermi 40, 00044 Frascati-IT; 3) DIID, University of Palermo, 90128 Palermo-IT; 4) IETCLaboratories, 6827 Brusino Arsizio-CH.

NB. Some data and figures presented at “2019 MIT Colloquium on CANR/LANR”, 23-24 March 2019, Cambridge-USA (DOI: 10.13140/RG.2.2.16626.76480); “3° Convegno Assisi nel Vento”, 17-19 May 2019, Assisi –Italy (DOI: 10.13140/RG.2.2.21906.91846).

ICCF22, September 8-13, 2019; Assisi (PG)-Italy

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Outline and Motivations

1) Explore, in some details, the role of D flux through specific sub-micrometric materials

(loaded by Deuterium) interacting, at their surface, with accelerated electrons and/or

ions, to produce AHE in a way as stable as possible, avoiding its reduction over time;

2) Tentative simplifications of control parameters: mainly (quite simple) electrical

stimulation, bipolar up to 1200 Vpp (at the moment), 50 Hz, by a counter electrode.

3) Description of new geometrical set-up, with the core of the reactor as homogeneous as

possible in respect to local temperature gradients inside the reactor: NO knots, Capuchin

knots, super-Capuchin knots, as developed by our group since 2015.

4) Local thermal gradients, due to specific geometrical assembling (like knots), although

don’t need extra energy to operate, are quite difficult to model (by computer);

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5) We need UNDERSTANDING of the effects: simplification (i.e. avoiding) of each extra

contributes, even if proved to be useful for AHE generation, is mandatory.

6) Roles of: a) Richardson’s (i.e. electron emission, due to the absolute temperature of

kind of material at the Anode surface) and Child-Langmuir laws (electron transport,

apart specific constant and surface area, are proportional to the Anode-Catode

Voltage^1.5 and distance^-2): both active at quite low pressures; b) Paschen regimes

(DC and even AC, mainly due to Deuterium and/or noble gas mixtures) operated at mild

pressures, as later detailed;

7) Results on AHE values and its stability over time: depend, among others, on counter-

electrode waveform, specially high frequency components (several times not-linear

components) when some proper high voltage thereshold are overcome.

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8) Results on spontaneous voltage (and current) generation by a third electrode kept

unconnected. The effect, although qualitatively reproducible and discovered since 2014

with even several tests perfomed by a third part (Mathieu Valat, Bob Greeiner, both

from MFMP, co-founders of Life Open Science “philosophy”), has to be fully understood.

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Starting points

A) In principle, to get some kind of anomalous effects (thermal and/or “nuclear”) in the experiments

using some specific elements (Pd, Ti, Ni, alloys,…) that interact with Hydrogen and/or their isotopes,

is quite simple: just allow that the Hydrogen is LARGELY absorbed on the surface (even bulk) of the

specific material, especially with nanometric dimensionality, and “force” the Hydrogen to move (i.e.

“flux”) inside/outside of the material, avoiding that the Hydrogen fully escape out (e.g. experiments

made by G. F. Fralick, Y. Iwamura, F. Celani, G. Preparata, M. Mc. Kubre,….). It was observed, some

times, that also large flux of electrons is beneficial to increase the effects.

B) Recently, in gaseous High Temperature LENR system we found and showed that, almost always, the

AHE, if and when obtained (under large operating difficulties), tends to decrease over time, until

reaches values close to Zero Watts: the system is self-stabilizing toward ZERO AHE. Periodic external

“excitation” to resume (at least) flux is needed to keep the AHE alive. Some details described both

at “2019 MIT Colloquium” (March 2019) and “Assisi nel Vento” meeting (May 2019).

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C) More generally, at least according to our experience/experimentations, we have conflicting

requirements about the operating conditions: it seems a target impossible to achive.

D) High pressures (as high as possible) of H2 (or D2) are needed to allow loading the active material:

historically pure Pd, Ti, Ni; now alloys like Ni-Cu at submicrometric size. Adoptedped by us Cu-Ni-

Mn alloy coated by large amounts of Fe, Sr, K, Mn (multilayer, nanometric). Hopefully produced

some Ultra Dense Hydrogen or Deuterium at the surface of metal (cfr. L. Holmlid’s experiments).

E) Low pressures are needed to allow emission of electrons, similarly to (old) vacuum tube devices (i.e.

Diode, Triode, ….) from the active material having Low Working Function, H loaded, at high

temperatures. But low pressures--high temperatures combinations cause the de-loading of stored H.

F) The use of mild pressures and quite high voltage (Paschen curve) in the counter electrode is a

compromise among such conflicting requirements. Obviously the distance among the 2 electrodes

has to be kept as low as possible (few millimeters) to avoid operations at prohibitive high voltages.

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Paschen curves (by Wikipedia, 2019)

Fig.1. Paschen curves obtained for helium, neon, argon, hydrogen and nitrogen, using the expression for the breakdown voltage (Vb) versus the pressure (p)*distance (d) values. Measured at RT, DC. For deeper studies: specific links to Wikipedia; arXiv (R. Massarczyk et al, 1612.07170v1; 2016, low temp. studies); Han S. Uhm et al. (J. of Korean Physical Society Vol. 24, Feb. 2003, pp. S989-S993; high temp. studies). Vertical=Voltage; Horizontal=Pressure (Torr; 760 Torr=1.0133 bars)* Distance (cm). Both Log scale.

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Short history about the specific use of Constantan and knots.

(Extracted also from: ICCF21, June 2018; IWAHLM13, October 2018; MIT 2019 Colloquium, March)

Anomalous Heat Effects (AHE) have been observed by us in wires of Cu55Ni44Mn1

(Constantan) exposed to H2 and D2 in multiple experiments along the last 9 years.

The Constantan, a quite low-cost and old alloy (developed around 1890 by E. Weston), has

the peculiarity to provide extremely large values of energy (1.56--3.16 eV) for the catalytic

reactions toward Hydrogen (and/or Deuterium) dissociation from molecular to atomic

state (H22H). In comparison, the most known and very costly Pd (a precious metal) can

provide only 0.424 eV of energy: computer simulation from S. Romanowsky et al., 1999.

The energy given out during fast recombination process is quite high (about 4.5 eV): one

of the largest among the chemical reactions. In deep space, at low Hydrogen pressures,

the measured temperature is 36000 K: equilibrium among dissociation vs recombination.

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Some H (according to resistance reduction value up to 20-25 %; first measurements by

German Scientists on 1989) is almost stored inside the Constantan lattice, after its

absorption at high temperatures (> 180°C), few bar of pressure, several hours.

We made systematic studies (and published most of the know-how obtained, in

agreement with Live Open Science approach followed by MFMP collaboration), since 2011,

to study the absorption behavior versus temperature, pressure and surface “shape”.

The amount of ratio among the active volume (i.e. the thickness of sub-micrometric one)

and the bulk (used mainly as support), increases reducing the diameter of the wire. A

qualitative sketch introduced by us (Fig. 2). We observed (by SEM) that, at least in our

experimental conditions of wires preparation, the thickness of active section is of the

order of 10-30 m. Main drawback is the easiness of the wire breaking at low

dimensionality (<100 m). Moreover such deleterious effect is worsened at the highest

(and most useful!!) temperatures (>700°C) operated in the test.

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Fig. 2_M. Qualitative sketch of the ratio among the “active region” (sub-micrometric sponge) for fast

Hydrogen absorption/storage (blue color, tickness 20 m), and the metallic bulk (brown color), changing

the initial diameter of the wire.

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Improvements in the magnitude and reproducibility of AHE were reported by the Authors

of the present work in the past and related to wire preparation and reactor design.

In facts, an oxidation of the wires by several hundred pulses of high intensity electrical

current (up to 10-20 kA/cm2, even neglecting skin effects present because fast rise time,

<1 s, of the pulses) in air (and related quenching) creates a rough surface (like sponge). It

is featured a sub-micrometric texture that proved particularly effective at inducing thermal

anomalies (once the H, D is absorbed/adsorbed) when both temperatures exceeds 300-

400 °C and proper kinds of non-equilibrium conditions are promoted. The effects increase

as temperatures are increased, until adverse self-sintering effects (almost out of control, at

the moment) damage the sponge structures and most of the AHE vanish.

The hunted effect appears also to be increased substantially by deposing segments of the

wire with a series of elements: Fe, Sr (via thermal decomposition of their nitrates)

properly mixed with a solution of KMnO4 (all diluted in acidic heavy-water solution).

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The magnetic proprieties of Constantan wires change dramatically after the coating of Fe

nitrate (further decomposed to FeOx) from “a-magnetic” to strong ferromagnetic. The

special geometry of Capuchin knot (see later-on), as speculation, could enhance such

aspects. It is noteworthy that FeOx are recently reported to have magnetic properties

enhanced up to 100-10000 times when at low dimensionality (10 micron down to 10 nm)

as in our specific fabrication procedures (multilayer).

Furthermore, an increase of AHE was observed after introducing the treated wires inside a

sheath made of borosilicate glass (mainly Si-B-Ca; BSC), and even more after impregnating,

the sheath with the same elements (Fe, Sr, K, Mn) used to coat the wires. Liquid nitrated

compounds were first dried and later-on decomposed to oxides by high temperature (400-

500 °C) treatments. The procedure was repeated several times: multilayer approach.

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Finally, AHE was augmented after introducing equally spaced knots (the knots were locally

coated with the mixture of Fe, Mn, Sr, K) to induce thermal gradients along the wire (knots

become very hot spots when a current is passed along the wire).

Interestingly, the coating appears to be nearly insulating and it is deemed being composed

of mixed oxides of the corresponding elements (mostly FeOx, SrO).

A) Having observed a degradation of the BSC fibers at high temperature, an extra sheath

made of quartz fibers was used to prevent the fall of degraded fibers from the first sheath,

i.e. made a sort of coaxial construction. Main drawback was its large dimensionality. We

recall that some specific borosilicate glass has the peculiarity of assorbing Atomic

Hydrogen (dissociated from molecular state by the Constantan), as discovered by Irving

Langmuir (Nobel Laureate, on 1928). In our procedures the possibility to have a “thank” of

atomic hydrogen, very close to the wire surface, is one of the main aspects.

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In 2014, the Authors introduced a second independent wire, “floating” in the reactor

chamber, and observed, just by chance, a weak electrical current (up to hundreds of A,

with several mV at the end of the wire), flowing in it while power was supplied to the first.

At that time the sheaths were NOT impregnated by nitrate/oxide mixtures, so, possible

leakage currents were unlucky to happen. The effect was also confirmed/certified (at

Frascati Laboratory by their own instrumentations and specific SW for data acquisition)

and (later-on) independently reproduced, by the MFMP group (M. Valat, B. Greeiner).

This current proved to be strongly related to the temperature of the first wire and clearly

turned to be the consequence of his Thermoionic Emission (where the treated wire

represents a Cathode and the second wire an Anode), according to the Richardson law.

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The key parameter of thermoionic emission is the Work Function (), usually 1.5-5 eV, for

electron emission, from the surface of the materials:

J=AgT2exp(-/KBT)

with:

J=emission current density [A/m2];

Ag= RA0 ; R is a correction factor depending on the material (0.5—1);

A0=(4qemekB2)/(h3)=1.2*106 [A/m2K2], Richardson constant

qe=1.6*10-19 C, electron charge;

me=5.11*105 eV, electron mass;

kB=8.617*10-5 eV/K, Boltzmann constant.

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Fig.3_M. Dependence of electron emission on Temperature (300--1300K) and Work Function (1--2.75

eV)

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The presence of the thermoionic effect and a spontaneous tension between the two wires

did strongly associate to AHE.

The thermoionic effect is enhanced, in our specific procedures, by deposition of Low

Working Function materials (LWFm), like SrO, at the surface of the Constantan’s wire,

several thin layers.

In the Cold Fusion-LENR-AHE studies the Researcher that first (1996) introduced,

intentionally, LWFm was Yasuhiro Iwamura at Mitsubishi Heavy Industries (Yokohama-

Japan). Since that time he used CaO and later-on also Y2O3, both in electrolytic and gas

diffusion experiments at mild (<80 °C) temperatures.

All these observations were reported at various Conferences, and tentative explanations

were provided for the observed effects.

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The presence of thermal and/or chemical gradients has been stressed as being of

relevance, especially when considering the noteworthy effect of knots on AHE.

The ICCF21 Conference, held on June 2018 (at Colorado State University), marked a

turning point: the scientific community did show a notable interest on the effects of knots

and wire treatments, further increasing the confidence on the described approach.

From that moment, attempts to further increase AHE focused on the introduction of

different types of knots, leading to the choice of the “Capuchin” type (see Fig. 3) and, very

recently, to the “advanced Capuchin knot”.

The knot design, specially Capuchin one, leads indeed to very hot spots along the wire and

features three areas characterized by a temperature delta up to several hundred degrees.

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Fig. 4_M. Photo, in DC, I=1900 mA, of a piece of Constantan wire having a diameter of 193 µm. Capuchin knots with 8 turns. Temperatures estimated by color. The dark area is at temperature <600°C, the external helicoidal section is at about 800 °C, the inmost section, linear, up to 1000 °C in some areas.

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Advanced Capuchin coil construction, main peculiarity of the reactor’s core

The construction of new geometry was quite complex and several measures were provided to fulfill the specific requirements of the experiments, several times conflicting each-other.

Some of the main problems/solution are resumed, as following:

B) The new system is (partially) based, about the main geometry of Constantan “turning”, on

the well-known methodologies adopted (since about 1930) for the construction of the

filaments of incandescent light bulbs (by Tungsten sintered wires).

C) In other words, the wires have a geometry of coils with both distance among spirals and

diameter of the coil as short as possible.

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D) To avoid short circuitry among adjacent spires, the wires are put inside insulating sheaths

able to withstand high temperatures, i.e. hybrid construction (up to 1200 °C, made by SiGi-

Favier Company, laboratories located in Italy and France).

E) The hybrid structure, made by alternating (at very short distance, <5 mm) bundles of

borosilicate glass fibers (diameter of each fiber is about 5 m, stable up to 750 °C) and

Quarz Alumina (stable up to 1200 °C), was developed because our specific request thanks

to a cross-collaboration among our group (in Frascati), a Methallurgical Company located

in the Nort-East of Italy (involved in LENR studies since 2011 and giving us also financial

support since that time) and the Sigi-Favier Company.

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F) As final effect, part of the energy emitted from the (incandescent) wire is self-

concentrated at the center of the coil where are located: a) the initial and final parts of the

wire, b) a thermometer (type K thermocouple, SS covered and electric insulated, for local

temperature measurement purposes), c) another wire (at large surface and inert in

respect to H adsorption) used as the Cathode or generally counter-electrode of the system.

G) The effect of (partial) reflection of IR emitted is reinforced by a SS316 tube that reflects

efficiently the temperature.

H) The construction is modular and the thick wall (3mm) glass reactor is the main container

of 3 independent type of wires, each into an independent SS tube. One wire is used as

general purposes test (made by Pt, identified as V1 because 100 m wire diameter).

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Fig.5_M. Overview of the assembling of the SS tube, each filled by coiled Constantan wire, except V1 (by Pt).

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Fig. 6_M. Details of the assembling of typical “Advanced Capuchin knot”: thermocouple and Anode wire.

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General assembling of the reactor, keep constant from 9 months,

to inter-compare results changing only the core.

a) Energy balance measurements by air flow calorimetry.

b) Calibration by a Joule heater put inside a Borosilicate glass tube, with the same dimension

of main reactor. Both glass tube are close each other and thermally connected by several

Al foil darkened (paint 900 °C type, emissivity close to 95%), inside the main insulating box.

c) In and out of air inlet at the same height, large vortexes are promoted just by geometry.

d) Monitored the speed of the fan (life-time rated at 5 years of continuous operation).

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Fig. 7_M. Photo of the reactor assembled, just before to be located into the air flow calorimeter.

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Fig. 8_M. Photo of the reactor, and calibrator (Ni-Cr wire) put inside the calorimeter (advanced version, 2

insulating and reflecting walls)

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Fig.9_M. Photo of the Calorimeter, air flow, just before closing the cover. Glass reactor protected by SS net.

The tick Al foil blackned, embracing the 2 glass tube, are not shown for clarity.

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Schematic drawing, Fig.10, of the new COAXIAL geometry of

each core of the reactor.

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9)

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Schematic of each core and auxiliary circuitry

Fig. 11. Schematich of each core, wires with the same length of 1700 mm and different compositions and diameters:

T1: Pt (99.9% purity), =127 m; stress realized, smooth surface.

T2: Constantan, =200 m; surface sponge-like, multilayer coating of Sr, Fe, K, Mn

T3: Constantan, =350 m; surface sponge-like, multilayer coating of Sr, Fe, K, Mn.

Fig. 12. DC polarization network, for low power (i.e. R/Ro) measurements (based on constant current diode J511) and High Power (based on 600V, 5A Diode).

Added several Zener diodes and resistances for protection purposes against possible excessive interferences due to AC High Voltages (up to +-600 Vp) on the counter electrodes.

Fig.13. Circuit for AC stimulation, mainly based on 2 low-power transformers in series and limiting resistor (10 kOhm) at the output.

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Fig. 11. Schematic of main component of reactor core V1, V2, V3. Support is a Fe tube covered

by, electrical insulating and net-styled (holes <<100 m), thin quartz-alumina sheath.

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Fig. 12. Schematic of the main circuitry adopted, both for R/Ro measurements (always connected to the wires) based on JFET J511 (Constant Current diode, 3 in parallel, each providing 4.7 mA of current) and main high power (by high power diode of 600V, 5A) to be injected along the wires, one each time.

The section at low power has several protection networks (based on Zener diodes and resistors), to avoid catastrophic failures due to unexpected pulses coming from the AC power (up to +-600 Vp) injected to the counter electrode to promote both Richardson (positive region of the wave, low pressures) and Paschen regime.

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Fig. 13. Circuitry to generate AC voltage (up to +-600 Vp), at low current (absolute limit 60 mA with 10 kOhm resistor) to promote both Richardson and Paschen regimes. The current injected has a typical value up to 10-15 mA peak and RMS value up to 5-6 mA, as measured by Fluke 187 multimeter (BW=100kHz). The RMS Voltage is of the order 250-280 V, as measured by Tektronix DMM916 Multimeter (BW=20 kHz). For higher accuracy, and better understanding of waveform, the signals at the end of 10 kOhm resistor are sent to a Fluke 198c Digital Scope (BW=100MHz).

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Some typical results

A) 3 Oscilloscope observation of waveform and related effects in respect to AHE, if any.

B) 3 Photo of some temperature-power-pressure results, raw data from log –book, in respect to operating point and AHE generation, if any.

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Fig. 15. Typycal excitation with NO effects in respect to AHE generation.

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Fig. 16. Typical exicitation at high temperature (>700 oC) but too-low pressure. Mild effect on AHE stability. Easy to deload Deuterium.

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Fig. 17. One of the best regimes (temperature-pressure) that optimized both the Richardson and Paschen regimes, with the largest AHE values reached (>14 W) by the V2 wire. The drawback is the limited range of operating regime. We are thinking to optimation by A.I. approach.

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Fig .18. Preliminary studies, at RT, to find the optimal pressure to can enter in the Paschen regime. It is clearly shown the effect on the local temperature increases inside the core of the reactor (TV2).

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Fig. 19. AC excitation, at condition close to optimal, always kept active. Core temperature of about 700 °C. Input power of about 80 W. AHE was stable for 24 H with an AHE of 11W. Later, changing the optimal point

(too-low pressure), it reduced to about 8 W.

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Fig. 20. Best result up to now obtained. Wire V2. AHE up to 14 W with 100 W of input. AC excitation <0.3 W. Atmosphere of Ar=D2, about 30 mbar of pressure. Several HF spikes on Paschen curve (negative side of oscilloscope). Later we got “gamma ray” alarm (>4 BKG). After few minutes a strong EMP interference happened (computer went out) and experiment ended. Some hours to restart everything.

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Spontaneous Voltage and current measurements

It was reconfirmed the effect, found on 2014 and independently tested by Matieu Valat and Bob Greeiner (MFMP project), of voltage drop, and current flowing, on a SINGLE constantan wire once adsorbed some amout of Deuterium.

A typical experiment, performed by using the wire V2 (=200 m; l=1700 mm; R= 27 Ohm at RT) is reported on Tab.1. The Cold side of the wire is at 21 °C, the Hot (identified as V2) is at temperatures as quoted.

Temperature V2 (°C) DV (mV), Rload=10 MOhm I (A), (DR=100 Ohm)

21 0.02 -1 208 -4.58 -36.5 236 -5.04 -39.8 261 -5.54 -42

285 -6.0 -47.6 305 -6.36 -47 317 -6.58 -47

Further studies, specially at higher temperatures (>350 °C) are needed to fully understand the effect.

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Conclusions

A) The efforts to simplify the excitation of our Constantan based reactor, using ONLY as control parameter a Voltage excitation at low current (few mA), seems to give a positive answer. Because pressure is a co-factor, some A.I. could be useful to manage them.

B) Nex step will be the increasing of the value of Voltage (now at about 1200 Vpp), key parameter for both the “electrons” and “ion” excitation.

C) Other control parameter can be the shape of the waveform and his frequency, now for simplicity just sinusoidal and almost symmetrical at 50 Hz, apart the “spontaneous spike”.

D) We guess that the excitation, apart promoting flux of deuterium in/out of the surface, could be useful also to avoid the weakening of cathalitic proprieties of surface, due to aging effects, as well know among the experts of “Cold Plasma”.

E) Obviously, once that the studies on voltage effect will be finished, we will resume also the previous intrinsic thermal non-equilibrium geometry (like “knots”), obviously modified and optimized thanks to new know-how acquired.

F) We are optimistic in respect to a practical use of AHE effects.

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Achwoldegments

A) We continue to be indebted with the Metallurgical Company, located at the Nort-East of Italy, for his continuos economical support (since 2011) and several “practical” suggestions to help solving several of the critical aspects in developing our non-conventional “AHE reactors”.

B) Some of expenses needed to attend the previous 2019 MIT meeting and repair of damaged instrumentations were provided by IFA (Water&Energy Company)-Italy. Some technical discussions about the possible role of RF excitation were stimulating to us.

C) We thank the Antropocene Institute (i.e. Carl Page and Frank Ling)-USA for providing economical support to 2 of our Collaborators to can attend ICCF22.

D) We thank Ideki Yoshino, CEO of Clean Planet Company, for providing economical support to another Membership of our group to can attend the ICCF22.

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Our group has been studying LENR phenomena in Constantan (Cu55Ni44Mn1) since 2011. In fact, this alloy captured our attention since it promotes

efficiently the dissociation of molecular Deuterium (D2) or Hydrogen (H2) to the atomic state, followed by a remarkable absorption capability.

Under certain conditions, this absorption is associated with exothermic phenomena exceeding by orders of magnitude the enthalpy of

conventional reactions. Constantan is also much cheaper than Palladium, has better mechanical properties and it is found in an ample variety of

applications. Similarly to the better studied Palladium, the occurrence of anomalous heat effects (AHE) in Constantan requires a loading with

Deuterium or Hydrogen and conditions of non-equilibrium. When the latter are absent, AHE is either reduced or tend to decline with time. This

observation led our group to investigate ways to increase non-equilibrium conditions. From 2016 we studied in particular the effect of surface

modification of the Constantan wires with coatings comprising elements able to modify the absorption behavior (i.e. Fe) and oxides with low work

function. We also developed certain geometrical arrangements of the wires (knots, capuchin knot and so-on) in order to induce local thermal

gradients and hot-spots. Moreover, the polarization of the wires (initially as cathode) with a power supply proved to be a versatile approach to

induce non-equilibrium conditions and AHE. In that respect, we have speculated that the electron emission from the wires may induce the

movement of active species (similarly to the Richardson effect – data presented at MIT in March 2019). This hypothesis seems to be confirmed by

the more recent finding that both the polarization of the Constantan as cathode or anode produces some AHE stimulus. The study of alternating

currents followed (50 Hz, 600V), and proved to be an effective trigger as well. These results have been presented at the ANV Meeting in Assisi (17-

19 May 2019), where we anticipated the findings of this presentation. In particular, we reported a remarkable AHE increase at reduced pressure,

when a gas discharge closely matching the Paschen-law occurs. Because of the promising results with the AC fields, we assembled the wires in a

different geometrical configuration, with the aim at maximizing the gas discharge phenomena (i.e. dielectric barrier discharges). This new

geometry comprises a Constantan wire with a coaxial counter electrode (a Fe thin tube insulated by SiO2 sheath). The Constantan wire is inserted

inside a sheath comprising glass Type_e and SiO2-Al2O3 fibers, and then coiled over the Fe counter electrode (=6mm) while keeping as low as

possible the distance between the electrodes (<2.5 mm). The presentation discusses the results obtained with the new assembly and the effect of

AC stimuli with Constantan wires of different thicknesses ( 200, 350 m) and length of 170 cm. The Constantan wires were studied up to 750 °C

and gas pressures ranging from 100 up to 2500 mbar.