George Collins - Academia.edu (original) (raw)

Papers by George Collins

Ensuring water quality that conforms to regulated standards is a challenging problem with multipl... more Ensuring water quality that conforms to regulated standards is a challenging problem with multiple dimensions, including cost, efficiency, and safety. For example, chemical techniques used for conventional drinking water treatment are usually effective, but often produce toxic by-products, such as trihalomethanes (THMs). This study describes the development of plasma technology as an alternative water treatment approach and in particular focuses on the challenges associated with the formation of plasmas in a dense medium such as water. Plasma treatment is highly attractive because the multiple reactive species produced (O • , OH • , O 3 , e − , O 2 − , O − , O 2 + etc.) are combined with UV light to work synergistically in the destruction of harmful microbes and other organic contaminants. Experiments with the RF-powered atmospheric pressure plasma in air have demonstrated a five log removal of Escherichia coli after just a few seconds of exposure, without significant heat generation. The fact that reactive species are generated without the addition of any harmful reagents and recombine immediately after turning off the device is a central feature of the approach. Recent experiments have focused on adapting the plasma for water treatment and have also demonstrated significant E. coli removal. The dense medium plasma is thus a promising method of treating water without the addition of chemicals, and may prove to be effective for the removal of other harmful microorganisms such Cryptosporidium, Salmonella, and Bacillus spores, as has been observed at atmospheric pressure. This study will describe the development of the RF-powered dense medium plasma for water treatment and the initial suite of results.

Applied Physics Letters, 1976

We report eight new ksa transitiori which span the wavelength region from 220 to 400 nm. Six of t... more We report eight new ksa transitiori which span the wavelength region from 220 to 400 nm. Six of the ultraviolet transitions are observed in Ne-Ag mixtura and two are observed in HcAg mixturrs. The 227.8and 224.3-m laser tmsitionsof Ag II, M 3D,-Sp 3f! and Sd ' So-5p ' Pt respectively, are the shortestwavelength cw laser transitioar reported in the literature to date. Output charactcrirtics of tbe ultmvinlet lasa transition 4d'Ss' 'G,4d*5p 'F!, at 318.1 nm. provides single-line peak output power of 350 mW. The output power does mt appear to saturate at the limit of our input current, 50 A.

Physics Letters A - PHYS LETT A, 1981

An applied longitudinal magnetic field is observed to decrease the equilibrium population of exci... more An applied longitudinal magnetic field is observed to decrease the equilibrium population of excited argon ion levels in a hollow cathode discharge, whereas the excited state populations of neutral argon atoms are not significantly altered. The longitudinal magnetic field is shown to decrease the effective density of beam electrons in the negative glow.

Physics Letters A

A cw Cd II laser has been demonstrated using electron beam excitation. Cw laser oscillation has b... more A cw Cd II laser has been demonstrated using electron beam excitation. Cw laser oscillation has been obtained on six transitions of Cd 11 in a He-Cd plasma. Output power as a function of electron beam discharge parameters has been investigated.

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures

... 4. Plane view microp3]otographs of self-developed patterns on poly-mers following exposure to... more ... 4. Plane view microp3]otographs of self-developed patterns on poly-mers following exposure to pulsed electron beami, through a stencil mask placed 25 ... 22 A. Novembre and TN Bowmcr, in Materials for Microlithograpky, edit-ed by С G. Wilson, LF Thomson, and JMJ Fre'chet ...

Unclassi f icd 2.. SECURITY CLASSIFICATION AUTHORITY 3. DISTRIBUTION/AVAILABILITY OF REPORT Appro... more Unclassi f icd 2.. SECURITY CLASSIFICATION AUTHORITY 3. DISTRIBUTION/AVAILABILITY OF REPORT Approvcd for public rltlasC; 2b. OECLASSIF ICATION/OOWNGRAOING SCHEDULE Distribution unlimited 4. PERFORMING ORGANIZATION REPORT NUMBER(S) 5. MONITORING ORGANIZATION REPORT NUMBER(S) AFOSR,/]RT h-! NAME OF PERFORMING ORGANIZATION 6b. OFFICE SYMBOL 7.. NAME OF MONITORING ORGANIZATION I 1 (If applicblte) * {s,.arci lnt itutc of Colorado AFOSR/NP 46c. ADDRESS (City. State and ZIP Code) 7b. ADDRESS (City. State and ZIP Code))rakt. (rtksidc Two, Suit.(Il no)XV'('g. 1 Call bcn tol,,rat,,d. "1,1 new lcctron gull. thait-h v. ,,, u' for las r cxcitation find also important ipplications in otlhr ar(,as of rt-starch, such as thl * procssing of microltctronic malltrial, as wc dcscribcd ill our rvitw art iclt, 1 \ppl. ['h s. 36 796, (1984).

Journal of Vacuum Science and Technology

Journal of the Optical Society of America, Oct 1, 1978

Aps Meeting Abstracts, Oct 1, 2008

The E-coli was inactivated using an atmospheric pressure microplasma in air. The microplasma was ... more The E-coli was inactivated using an atmospheric pressure microplasma in air. The microplasma was generated between two parallel aluminum rods are 5 cm long, 3 mm in diameter, maintain 200 mu\mu mum wide gaps between two electrodes, and covered with nanoporous alumina ...

Final Report Sep 1986 Mar 1989 Colorado State Univ Fort Collins Dept of Electrical Engineering, May 1, 1989

We report the generation of microplasmas that use electrodes with nanoporous dielectric surfaces.... more We report the generation of microplasmas that use electrodes with nanoporous dielectric surfaces. The electrodes used in the dielectric barrier discharge are made of aluminum rods or plates covered with nanoporous alumina films, sim\sim sim80 mu\mu mum thick and mean ...

This study compared and contrasted biological tissue removal via plasma chemistry compared and co... more This study compared and contrasted biological tissue removal via plasma chemistry compared and contrasted with standard electrosurgery. With high speed image capture of the tissue division, the mechanism differences between the two methods are evident. While standard electrosurgery removes tissues with thermal vaporization during arc events, the plasma application modifies the tissue structure during plasma exposure. The thermal damage zones