HPS 66th Annual Meeting

Phoenix, Arizona
July 25th-29th 2021

Single Session

[Schedule Grid]

VTU-D - Special Session: Nonionizing Radiation

   10:10 - 12:00

VTU-D.0   10:10  Introduction

VTU-D.1   10:20  ANSI Z136.8 LASER SAFETY FOR RESEARCHERS, second edition RECOGNIZING AN UNMET SAFETY GUIDEANCE NEED KL Barat*, Laser Safety Solutions ; Ke Barat

Abstract: The major laser standard in the United States is the ANSI Z136.1 Safe Use of Lasers. This standard tends to provide guidance as if all lasers are commercial products that meet government laser product safety requirements. The ANSI Z136.8 Safe use of laser in research, development and testing moves away from that approach. This year the second edition of Z136.8 has been published. Any user or Laser Safety Officer (LSO) is aware that laser used in the research environment, particular in development stage does not meet all the requirements of a certified laser product and many area controls are not always applicable or relevant. As an example, diode lasers on a breadboard (especially one that can be moved around) the idea of an emergency shut off switch is questionable. Especially in cases where the open beam path maybe a centimeter or less. The ANSI Z136.8, recognizes the example above and gives the LSO support from the standard if they decide not to use such a device. Another good example is in the topic of training. The standard requires documented on the job training. Which any user will tell you it is on site training where safety takes place. Institutional laser training requirements are really only a first step of hazard awareness. Last example is just a common-sense item. The Z136.1 for access control of class 4 laser areas, support the use of room entryway interlocks. But does not require any operational check to see if they are functioning. If the entryway interlock is a safety device, don’t you think there would be some requirement to test its functionality? ANSI Z136.8 covers all these topics and much more. This presentation is to acquaint one with this standard and its newest edition elements.

VTU-D.2   10:40  Practical laser safety calculations: Case studies in supercontinuum lasers MA Spencer*, Massachusetts Institute of Technology ; FW McWilliams, Massachusetts Institute of Technology

Abstract: For a typical monochromatic laser system, determination of the appropriate eye protection is relatively straightforward, requiring only the calculation of the maximum permissible exposure (MPE) to laser radiation at that wavelength and the maximum irradiance (or radiant exposure) to which a user might be exposed. From these two quantities the optical density (OD) of eyewear which will provide sufficient protection to reduce the accessible irradiance below the MPE can be determined. In a system with nonlinear optics that change the wavelength, for example, frequency-doubled Nd:YAG (532nm) where the fundamental mode (1064nm) is still present, the calculation becomes more complex. In the extreme case, supercontinuum lasers emit light in a very broad wavelength range, making calculation of the MPE quite difficult. Worse, since these “laser rainbows” often cover the entire visible spectrum, eyewear must be carefully selected such that users can still see while wearing it. Following an overview of laser safety calculations in systems of increasing complexity, we present a method for calculating the MPE for a laser with an arbitrary spectral content (broad wavelength range or many discrete wavelengths) as well as a method for determining appropriate laser eye protection for such a laser. In addition, other novel methods of protection are presented.

VTU-D.3   11:15  Modeling a Thermoacoustic-based High Power Microwave Directed Energy Exposure Detection System JJ Frey*, Air Force Institute of Technology

Abstract: This presentation will discuss design considerations for a potential detection and measurement technique that could provide operational awareness of high power microwave (HPM) directed energy weapon (DEW) exposure, leveraging thermoacoustic (TA) wave generation as the field interaction mechanism. The HPM electromagnetic frequency (EMF) regime, used in applications in both the counter-materiel and non-lethal counter-personnel design space, presents real-time personnel exposure warning challenges due to the potentially wide variation in time and frequency domain characteristics of the incident beam. As with other EM-thermal interactions, the thermoacoustic wave effect provides the potential to determine energy and power deposition without the need to measure ambient field intensity values. A lossy dielectric medium subject to pulsed HPM was computationally modeled using the commercial finite element method multi-physics simulation software package COMSOL. The simulation was used to explore the impacts of various material properties on TA signal output as a function of simulated incident field power density, EM frequency, pulse length and pulse repetition frequency, thereby informing the selection of system components for the further development of a full TA-based HPM detection chain.

VTU-D.4   11:35  Did Microwaves Harm US Employees At Its Embassy in Havana? KR Foster*, University of Pennsylvania

Abstract: Since 2016 a controversy has developed about a possible attack on US personnel at the U.S. Embassy in Havana. The incidents occurred in the employees' residences or, in some cases, in hotel rooms. Similar events have been reported by US consulate staff in Tashkent Uzbekistan and Guangzhou, China, as well as by members of the Canadian diplomatic community in Havana. The events were characterized by a variety of reported symptoms, initially a "perceived loud sound, a sensation of intense pressure or vibration in the head, and pain in the ear or more diffusely in the head" followed a few days later by cognitive deficits and vestibular disturbances and other symptoms. No physical agent has been identified as a cause of the symptoms, which remain unexplained. This talk will review all publicly available information about the incident, including medical followups of embassy personnel reporting symptoms, a review of medical records by the CDC, a report issued by a panel of the National Academy of Sciences, Engineering and Medicine (NASEM), and a recently declassified report by the Accountability Review Board (ARB) of the Department of State. The NASEM panel considered that the most plausible mechanism to explain staff symptoms was directed, pulsed radio frequency (RF) energy. Other proposed explanations include an attack by an acoustic weapon, environmentally caused illness, and mass psychogenic illness. This talk will conclude with a critical assessment of the various theories for the problems and a summary of the critique in the ARB report of the handling of the issue by the Department of State. Mary52

VTU-D.5   11:55  Section Awards

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