Iodine monochloride/molecular iodine as the iodine source...

Details Iodine monochloride/molecular iodine as the iodine source... Iodine monochloride/molecular iodine as the iodine source...

1999-06-03

2002-04-23

Scott, Jr., Leon (Department: 2881)

Coherent light generators

Particular pumping means

Chemical

Reexamination Certificate

active

06377600

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to chemical laser systems, and more particularly to the use of iodine monochloride and molecular iodine as the iodine source for chemical oxygen iodine laser (COIL) systems.
2. Discussion of the Related Art
The fact that an atom will emit a photon of radiation when one of its electrons drops to a lower energy state has enabled the laser to be employed in a number of military, industrial, and medical applications. The term “laser” is an acronym for light amplification by stimulated emission of radiation. In its simplest form, a laser consists of a rod of transparent crystal or a tube filled with gas or liquid. A mirror is placed at one end and a half-silvered mirror at the other end. The laser is then “pumped” by adding energy, e.g., by shining another light source into it, by adding electrical energy, or by stimulating a chemical reaction. This process raises electrons in the laser to higher energy states.
During the pumping process, some of the electrons will spontaneously fall back to a lower energy state, emitting photons. The photons that travel toward the sides of the laser are quickly lost, but those traveling along the length of the rod or tube are reflected back by the mirrors. This activity generally occurs in the area commonly referred to as the laser gain region. When these photons strike other excited atoms, they stimulate those atoms to release photons of the exact same energy level (or wavelength), which travel in the same direction as the stimulating photons. The result is an intense, highly focused beam of light escaping through the half-silvered end of the laser. This light beam is generally referred to as a beam of high energy coherent radiation, or more commonly, a laser beam.
Because the photon wavelength is determined by the characteristics of the atoms in the lasing material, laser light is of a single wavelength. Because laser light travels in a tight beam, it can carry a great deal of energy over a great distance without significant loss. With respect to recent developments in laser technology, there has been increased interest in chemical laser systems, especially COIL systems.
The COIL system was initially developed for military applications; however, recent attention has turned to potential industrial uses of COIL systems, such as metal cutting applications.
In a COIL system, chlorine gas reacts with a solution of basic hydrogen peroxide (i.e., H
2
O
2
) (usually KOH or NaOH mixed with hydrogen peroxide) to produce a gaseous flow of excited oxygen, also referred to as singlet delta oxygen or singlet molecular oxygen (designated as O
2
*, O
2
(
1
&Dgr;), as well as by other symbols). This gaseous flow of singlet delta oxygen collides (typically at speeds approaching or even exceeding the speed of sound) with iodine gas molecules (i.e., I
2
), dissociating them and subsequently exciting the resulting iodine atoms (i.e., I), which lase at 1.315 &mgr;m. The major laser byproducts are various salts (e.g., NaCl or KCl) and heat. The small amounts of iodine can be scrubbed from the output.
FIG. 1
illustrates a highly simplified schematic of the intended operation of a conventional COIL system
10
. The initial step is to generate the singlet delta oxygen. This is accomplished by providing a source
12
of basic hydrogen peroxide, typically in liquid form, and a source
14
of molecular chlorine, typically in gaseous form. These two materials are then charged or injected into a singlet delta oxygen generator
16
through appropriate manifold/conduit assemblies
18
,
20
, respectively. The resulting exothermic reaction between the basic hydrogen peroxide liquid and the molecular chlorine gas produces the gaseous singlet delta oxygen, as well as several by-products, such as salt and heat. The heat can be removed by appropriate devices such as a heat exchanger (not shown), and the salt can be removed by appropriate devices such as a scrubber (not shown). The skilled artisan will appreciate that various well-known auxiliary components of the conventional COIL system
10
have been omitted for ease of illustration.
Once the gaseous singlet delta oxygen is generated, it is then charged or injected in flow form into a mixing nozzle
22
at the appropriate time. The mixing nozzle
22
has a throat portion
23
which generally divides the mixing nozzle
22
into a subsonic zone
24
and a supersonic zone
26
; that is, the flow of gaseous singlet delta oxygen is subsonic in one portion of the mixing nozzle
22
and supersonic at the other portion of the mixing nozzle
22
. The mixing of reactants is typically done in the subsonic zone
24
.
A molecular iodine generator
28
is in communication with the mixing nozzle
22
by an appropriate manifold/conduit assembly
30
. At the appropriate time, gaseous molecular iodine is then charged or injected into the mixing nozzle
22
in such a manner so as to let it “pool” before completely mixing with the singlet delta oxygen gas flowing from the singlet delta oxygen generator
16
. The slight delay in mixing due to this “pooling” permits the singlet delta oxygen to dissociate only some of the molecular iodine on the edge of the “pool” and thus initiate the chain reaction dissociation of molecular iodine by the product atomic iodine. However, in this “pooling” process, significant singlet delta oxygen is nonetheless lost due to excess reaction with molecular oxygen or deactivation with water, iodine, liquid or solid surfaces, or other loss mechanisms.
The primary reactions taking place in connection with the conventional COIL system
10
are as follows:
(1) I
2
+O
2
*→I
2
*+O
2
. That is, a mole of molecular iodine reacts with a mole of singlet delta oxygen to produce a mole of excited molecular iodine and a mole of molecular oxygen.
(2) I
2
*+O
2
*→2I+O
2
. That is, a mole of excited molecular iodine reacts with a mole of singlet delta oxygen to produce a two moles of atomic iodine and a mole of molecular oxygen.
(3) I+O
2
*→I*+O
2
. That is, a mole of atomic iodine reacts with a mole of singlet delta oxygen to produce a mole of excited atomic iodine and a mole of molecular oxygen.
(4) I*→I+h&ngr;. That is, a mole of excited atomic iodine releases a mole equivalent of photons (h&ngr;), thus producing a mole of atomic iodine.
The singlet delta oxygen gas flow initially contacts the gaseous molecular iodine “pool” at subsonic speed; however, the singlet delta oxygen gas flow is quickly brought up to near supersonic or even supersonic speed (via appropriate devices such as a venturi) and is expelled out through the mixing nozzle
22
into the area known as the laser gain region
32
of the laser cavity
33
. It is in this area where the excited atomic iodine releases its photon. The released photon is then reflected many times between a set of mirrors
34
, the first mirror
36
being fully reflective, the second mirror
38
being partially reflective. The reflected photons eventually form a laser beam
40
, which is transmitted through the partially reflective mirror
38
at a wavelength of 1.315 &mgr;m. Any remaining chemical species are removed from the laser gain region
32
by a combination of exhaust assemblies (not shown) and scrubber assemblies (not shown) in order to avoid contamination of the laser's mirrors
34
.
COIL systems have long been known to output less laser power than is theoretically available from the singlet delta oxygen leaving the generator. There are a number of proposed kinetic explanations for this, as well as several proposed or alternative approaches to increasing the output laser power. The advantages of enhanced power extraction from a given generator are substantial in the weight, volume and complexity of nearly all proposed applications of COIL systems.
Iodine monochloride has been suggested as a replacement for molecular iodine for COIL systems. It was found that under certain circumstances, conventional COIL systems were suffering from c

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