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72-549: The detector was turned on in May 1999, and was turned off on 28 November 2006. The SNO collaboration was active for several years after that analyzing the data taken. The director of the experiment, Art McDonald , was co-awarded the Nobel Prize in Physics in 2015 for the experiment's contribution to the discovery of neutrino oscillation . The underground laboratory has been enlarged into

144-516: A B.Sc. in physics in 1964 and M.Sc. in physics in 1965 from Dalhousie University in Nova Scotia . He then obtained his Ph.D. in physics in 1969 from the California Institute of Technology . McDonald cited a high school math teacher and his first-year physics professor at Dalhousie as his inspirations for going into the field of physics. Art McDonald worked as a research officer at

216-448: A particle counter and microorganisms detected and counted through environmental monitoring methods . Polymer tools used in cleanrooms must be carefully determined to be chemically compatible with cleanroom processing fluids as well as ensured to generate a low level of particle generation. When cleaning, only special mops and buckets are used. Cleaning chemicals used tend to involve sticky elements to trap dust, and may need

288-471: A "tunnel" design in which there are spaces called "service chases" that serve as air plenums carrying the air from the bottom of the room to the top so that it can be recirculated and filtered at the top of the cleanroom. Cleanrooms maintain particulate-free air through the use of either HEPA or ULPA filters employing laminar or turbulent airflow principles. Laminar, or unidirectional, airflow systems direct filtered air downward or in horizontal direction in

360-554: A cleanroom in constant motion, although not all in the same direction. The rough air seeks to trap particles that may be in the air and drive them towards the floor, where they enter filters and leave the cleanroom environment. US FDA and EU have laid down stringent guidelines and limits to ensure freedom from microbial contamination in pharmaceutical products. Plenums between air handlers and fan filter units , along with sticky mats , may also be used. In addition to air filters, cleanrooms can also use ultraviolet light to disinfect

432-432: A cleanroom is usually restricted to those wearing a cleanroom suit , including the necessary machinery. In cleanrooms in which the standards of air contamination are less rigorous, the entrance to the cleanroom may not have an air shower. An anteroom (known as a "gray room") is used to put on cleanroom clothing. This practice is common in many nuclear power plants, which operate as low-grade inverse pressure cleanrooms, as

504-456: A collaborating institution, Chalk River Laboratories led the construction of the acrylic vessel that holds the heavy water, and Atomic Energy of Canada Limited was the source of the heavy water. 46°28′30″N 81°12′04″W  /  46.47500°N 81.20111°W  / 46.47500; -81.20111 Arthur B. McDonald Arthur Bruce McDonald , CC OOnt ONS FRS FRSC P.Eng (born August 29, 1943)

576-529: A constant stream towards filters located on walls near the cleanroom floor or through raised perforated floor panels to be recirculated. Laminar airflow systems are typically employed across 80% of a cleanroom ceiling to maintain constant air processing. Stainless steel or other non shedding materials are used to construct laminar airflow filters and hoods to prevent excess particles entering the air. Turbulent, or non-unidirectional, airflow uses both laminar airflow hoods and nonspecific velocity filters to keep air in

648-593: A conversion of part of its Cambridge, Ohio facilities in February 1961. Totalling 70,000 square feet, it was used to prepare control equipment for the Minuteman ICBM missiles. The majority of the integrated circuit manufacturing facilities in Silicon Valley were made by three companies: MicroAire, PureAire, and Key Plastics. These competitors made laminar flow units, glove boxes, cleanrooms and air showers , along with

720-496: A detector for solar neutrinos. Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one reaction sensitive to all neutrino flavours, the other sensitive to only the electron neutrino. Thus, such a detector could measure neutrino oscillations directly. Chen, Professor George Ewan, Professor David Sinclair, McDonald, and 12 other scientists formed the original Sudbury Neutrino Observatory (SNO) collaboration to exploit this idea in 1984. SNO

792-621: A leader in astroparticle physics. In the spring of 2020, amid the COVID-19 pandemic and the ensuing shortages, McDonald became one of the leaders of a project to mass-produce mechanical ventilators at low cost. McDonald has stated that the project was initiated by Princeton Professor Cristiano Galbiati who was locked down in Milan , Italy. He inspired action by his colleagues on the DarkSide-20k Dark Matter physics experiment after recognizing

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864-607: A permanent facility and now operates multiple experiments as SNOLAB . The SNO equipment itself was being refurbished as of February 2017 for use in the SNO+ experiment. The first measurements of the number of solar neutrinos reaching the Earth were taken in the 1960s, and all experiments prior to SNO observed a third to a half fewer neutrinos than were predicted by the Standard Solar Model . As several experiments confirmed this deficit

936-432: A reduced reliance on chemical disinfectants and the extension of HVAC filter life. Some cleanrooms are kept at a positive pressure so if any leaks occur, air leaks out of the chamber instead of unfiltered air coming in. This is most typically the case in semiconductor manufacturing, where even minute amounts of particulates leaking in could contaminate the whole process, while anything leaking out would not be harmful to

1008-404: A second step with light molecular weight solvents to clear. Cleanroom furniture is designed to produce a minimum of particles and is easy to clean. A cleanroom is as much a process and a meticulous culture to maintain, as it is a space as such. The greatest threat to cleanroom contamination comes from the users themselves. In the healthcare and pharmaceutical sectors, control of microorganisms

1080-402: A small cross section for neutrons, but when neutrons are captured by a deuterium nucleus, a gamma ray ( photon ) with roughly 6 MeV of energy is produced. The direction of the gamma ray is completely uncorrelated with the direction of the neutrino. Some of the neutrons produced from the dissociated deuterons make their way through the acrylic vessel into the light water jacket surrounding

1152-552: A supernova are released earlier than the photons, it is possible to alert the astronomical community before the supernova is visible. SNO was a founding member of the Supernova Early Warning System (SNEWS) with Super-Kamiokande and the Large Volume Detector . No such supernovae have yet been detected. The SNO experiment was also able to observe atmospheric neutrinos produced by cosmic ray interactions in

1224-524: A whole. Recirculating vs. one pass cleanrooms Recirculating cleanrooms return air to the negative pressure plenum via low wall air returns. The air then is pulled by HEPA fan filter units back into the cleanroom. The air is constantly recirculating and by continuously passing through HEPA filtration removing particles from the air each time. Another advantage of this design is that air conditioning can be incorporated. One pass cleanrooms draw air from outside and pass it through HEPA fan filter units into

1296-415: Is filtered and cooled by several outdoor air handlers using progressively finer filters to exclude dust. Within, air is constantly recirculated through fan units containing high-efficiency particulate absorbing filters ( HEPA ), and/or ultra-low particulate air ( ULPA ) filters to remove internally generated contaminants. Special lighting fixtures, walls, equipment and other materials are used to minimize

1368-729: Is a Canadian astrophysicist . McDonald is the director of the Sudbury Neutrino Observatory Collaboration and held the Gordon and Patricia Gray Chair in Particle Astrophysics at Queen's University in Kingston, Ontario from 2006 to 2013. He was awarded the 2015 Nobel Prize in Physics jointly with Japanese physicist Takaaki Kajita . Art McDonald was born on August 29, 1943, in Sydney , Nova Scotia . He graduated with

1440-664: Is a co-recipient of the 2007 Benjamin Franklin Medal in Physics, the 2015 Nobel Prize in Physics , and the Breakthrough Prize in Fundamental Physics in 2016 for the discovery of neutrino oscillations and demonstrating that neutrinos have mass. Professor McDonald is now participating in research with the SNO+ and DEAP-3600 experiments at SNOLAB, an expanded underground laboratory at the original SNO underground site and with

1512-410: Is common to all cleanrooms is strict control of airborne particulates , possibly with secondary decontamination of air, surfaces, workers entering the room, implements, chemicals, and machinery. Sometimes particulates exiting the compartment are also of concern, such as in research into dangerous viruses , or where radioactive materials are being handled. First, outside air entering a cleanroom

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1584-553: Is detectable. The proton which is produced does not have enough energy to be detected easily. The electrons produced in this reaction are emitted in all directions, but there is a slight tendency for them to point back in the direction from which the neutrino came. In the neutral current interaction, a neutrino dissociates the deuteron, breaking it into its constituent neutron and proton. The neutrino continues on with slightly less energy, and all three neutrino flavours are equally likely to participate in this interaction. Heavy water has

1656-466: Is dominated by electron neutrinos, and this is the channel through which the Super-Kamiokande (Super-K) detector can observe solar neutrinos. This interaction is the relativistic equivalent of billiards , and for this reason the electrons produced usually point in the direction that the neutrino was travelling (away from the sun). Because this interaction takes place on atomic electrons it occurs with

1728-592: Is expressed in the following table. These concentrations will lead to large air sample volumes for classification. Sequential sampling procedure may be applied; see Annex D. Concentration limits are not applicable in this region of the table due to very high particle concentration. Sampling and statistical limitations for particles in low concentrations make classification inappropriate. Sample collection limitations for both particles in low concentrations and sizes greater than 1 μm make classification at this particle size inappropriate due to potential particle losses in

1800-412: Is important, especially microorganisms likely to be deposited into the air stream from skin shedding . Studying cleanroom microflora is of importance for microbiologists and quality control personnel to assess changes in trends. Shifts in the types of microflora may indicate deviations from the "norm" such as resistant strains or problems with cleaning practices. In assessing cleanroom microorganisms,

1872-427: Is located at the end of a 1.5-kilometre-long (0.9 mi) drift , named the "SNO drift", isolating it from other mining operations. Along the drift are a number of operations and equipment rooms, all held in a clean room setting. Most of the facility is Class 3000 (fewer than 3,000 particles of 1 μm or larger per 1 ft of air) but the final cavity containing the detector is an even stricter Class 100 . In

1944-646: Is not carried out, but room AHU is on). BS 5295 is a British Standard . BS 5295 Class 1 also requires that the greatest particle present in any sample can not exceed 5 μm. BS 5295 has been superseded, withdrawn since the year 2007 and replaced with "BS EN ISO 14644-6:2007". USP 800 is a United States standard developed by the United States Pharmacopeial Convention (USP) with an effective date of December 1, 2019. In hospitals , theatres are similar to cleanrooms for surgical patients' operations with incisions to prevent any infections for

2016-453: Is preferred. Buffed stainless steel or powder-coated mild steel sandwich partition panels and ceiling panel are used instead of iron alloys prone to rusting and then flaking . Corners like the wall to wall, wall to floor, wall to ceiling are avoided by providing coved surface , and all joints need to be sealed with epoxy sealant to avoid any deposition or generation of particles at the joints, by vibration and friction . Many cleanrooms have

2088-431: Is well isolated, well controlled from contamination , and actively cleansed. Such rooms are commonly needed for scientific research and in industrial production for all nanoscale processes, such as semiconductor manufacturing. A cleanroom is designed to keep everything from dust to airborne organisms or vaporised particles away from it, and so from whatever material is being handled inside it. A cleanroom can also prevent

2160-518: The CERN Open Hardware Licence . The project received the support of Prime Minister Justin Trudeau who anticipated an initial order of 30,000 to Canadian hospitals from several suppliers. An order has been placed for 10,000 units with Vexos, Markham. Cleanroom A cleanroom or clean room is an engineered space that maintains a very low concentration of airborne particulates . It

2232-819: The Chalk River Nuclear Laboratories northwest of Ottawa from 1969 to 1982. He became professor of physics at Princeton University from 1982 to 1989, leaving Princeton to join Queen's University where he was a professor from 1989 to 2013. McDonald was a visiting scientist at the European Organization for Nuclear Research (CERN) in Geneva in 2004. In 2013 McDonald became a professor emeritus of Queen's University in Kingston, Canada . He continues to be active in basic research in Neutrinos and Dark Matter at

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2304-531: The International Organization for Standardization (ISO). The former applies to cleanrooms in general (see table below), the latter to cleanrooms where biocontamination may be an issue. Since the strictest standards have been achieved only for space applications, it is sometimes difficult to know whether they were achieved in vacuum or standard conditions. ISO 14644-1 defines the maximum concentration of particles per class and per particle size with

2376-539: The SNOLAB underground Laboratory and was a past member of the board of the Perimeter Institute for Theoretical Physics . His visiting positions include CERN , University of Washington (1978), Los Alamos National Laboratory (1981), University of Hawaii (2004, 2009), University of Oxford (2003, 2009), Queen's University (1988). Physicists have been investigating whether or not neutrinos have mass. Since

2448-523: The University of California at Irvine first pointed out the advantages of using heavy water as a detector for solar neutrinos. Unlike previous detectors, using heavy water would make the detector sensitive to two reactions, one reaction sensitive to all neutrino flavours, the other reaction sensitive to only electron neutrino. Thus, such a detector could measure neutrino oscillations directly. A location in Canada

2520-413: The charged current interaction, a neutrino converts the neutron in a deuteron to a proton . The neutrino is absorbed in the reaction and an electron is produced. Solar neutrinos have energies smaller than the mass of muons and tau leptons , so only electron neutrinos can participate in this reaction. The emitted electron carries off most of the neutrino's energy, on the order of 5–15  MeV , and

2592-671: The humidity to such low levels that extra equipment like air ionizers are required to prevent electrostatic discharge problems. This is a particular concern within the semiconductor business, because static discharge can easily damage modern circuit designs. On the other hand, active ions in the air can harm exposed components as well. Because of this, most workers in high electronics and semiconductor facilities have to wear conductive boots while working. Low-level cleanrooms may only require special shoes, with completely smooth soles that do not track in dust or dirt. However, for safety reasons, shoe soles must not create slipping hazards. Access to

2664-550: The 1960s, Whitfield's modern cleanroom had generated more than US$ 50 billion in sales worldwide (approximately $ 483 billion today). By mid-1963, more than 200 U.S. industrial plants had such specially constructed facilities—then using the terminology “White Rooms,” “Clean Rooms,” or “Dust-Free Rooms”—including the Radio Corporation of America, McDonnell Aircraft, Hughes Aircraft, Sperry Rand, Sylvania Electric, Western Electric, Boeing, and North American Aviation. RCA began such

2736-637: The DarkSide-20k collaboration developing an experiment at the underground laboratory near Gran Sasso , Italy. The Arthur B. McDonald Canadian Astroparticle Physics Research Institute was inaugurally named the Canadian Particle Astrophysics Research Centre before renaming itself the Arthur B. McDonald Canadian Astroparticle Physics Research Institute in May 2018, in recognition of Dr. Arthur B. McDonald's trailblazing work making Canada

2808-426: The accelerated electron can be detected through Cherenkov radiation. In the elastic scattering interaction, a neutrino collides with an atomic electron and imparts some of its energy to the electron. All three neutrinos can participate in this interaction through the exchange of the neutral Z boson , and electron neutrinos can also participate with the exchange of a charged W boson . For this reason this interaction

2880-405: The air using a corona discharge . Static discharge is of particular concern in the electronics industry, where it can instantly destroy components and circuitry. Equipment inside any cleanroom is designed to generate minimal air contamination. The selection of material for the construction of a cleanroom should not generate any particulates; hence, monolithic epoxy or polyurethane floor coating

2952-463: The air. UV devices can be fitted into ceiling light fixtures and irradiate air, killing potentially infectious particulates , including 99.99 percent of airborne microbial and fungal contaminants. UV light has previously been used to clean surface contaminants in sterile environments such as hospital operating rooms. Their use in other cleanrooms may increase as equipment becomes more affordable. Potential advantages of UV-based decontamination includes

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3024-479: The atmosphere. Due to the limited size of the SNO detector in comparison with Super-K, the low cosmic ray neutrino signal is not statistically significant at neutrino energies below 1  GeV . Large particle physics experiments require large collaborations. With approximately 100 collaborators, SNO was a rather small group compared to collider experiments . The participating institutions have included: Although no longer

3096-454: The chemical tanks and benches used in the "wet process" building of integrated circuits. These three companies were the pioneers of the use of Teflon for airguns, chemical pumps, scrubbers, water guns, and other devices needed for the production of integrated circuits . William (Bill) C. McElroy Jr. worked as an engineering manager, drafting room supervisor, QA/QC, and designer for all three companies, and his designs added 45 original patents to

3168-731: The cleanroom. The air then leaves through exhaust grills. The advantage of this approach is the lower cost. The disadvantages are comparatively shorter HEPA fan filter life, worse particle counts than a recirculating cleanroom, and that it cannot accommodate air conditioning. In order to minimize the carrying of particulate by a person moving into the cleanroom, staff enter and leave through airlocks (sometimes including an air shower stage) and wear protective clothing such as hoods , face masks, gloves, boots, and coveralls . Common materials such as paper , pencils , and fabrics made from natural fibers are often excluded because they shed particulates in use. Particle levels are usually tested using

3240-405: The concentration is too low or too high to be practical to test for, but such blanks should not be read as zero. Because 1 m is about 35 ft , the two standards are mostly equivalent when measuring 0.5 μm particles, although the testing standards differ. Ordinary room air is around class 1,000,000 or ISO 9. ISO 14644-1 and ISO 14698 are non-governmental standards developed by

3312-590: The concentration of airborne particles, equal to and larger than the specified sizes, at designated sampling locations. Small numbers refer to ISO 14644-1 standards, which specify the decimal logarithm of the number of particles 0.1 μm or larger permitted per m of air. So, for example, an ISO class 5 cleanroom has at most 10 particles/m . Both FS 209E and ISO 14644-1 assume log-log relationships between particle size and particle concentration. For that reason, zero particle concentration does not exist. Some classes do not require testing some particle sizes, because

3384-531: The considered particle size which is rounded to the nearest whole number, using no more than three significant figures, N {\displaystyle {\text{N}}} is the ISO class number, D {\displaystyle {\text{D}}} is the size of the particle in μ {\displaystyle \mu } m and 0.1 is a constant expressed in μ {\displaystyle \mu } m. The result for standard particle sizes

3456-588: The director of SNO Art McDonald with the Benjamin Franklin Medal in Physics. In 2015 the Nobel Prize for Physics was jointly awarded to Arthur B. McDonald, and Takaaki Kajita of the University of Tokyo, for the discovery of neutrino oscillations. The SNO detector would have been capable of detecting a supernova within our galaxy if one had occurred while the detector was online. As neutrinos emitted by

3528-416: The effect became known as the solar neutrino problem . Over several decades many ideas were put forward to try to explain the effect, one of which was the hypothesis of neutrino oscillations . All of the solar neutrino detectors prior to SNO had been sensitive primarily or exclusively to electron neutrinos and yielded little to no information on muon neutrinos and tau neutrinos . In 1984, Herb Chen of

3600-744: The escape of materials. This is often the primary aim in hazardous biology , nuclear work , pharmaceutics and virology . Cleanrooms typically come with a cleanliness level quantified by the number of particles per cubic meter at a predetermined molecule measure. The ambient outdoor air in a typical urban area contains 35,000,000 particles for each cubic meter in the size range 0.5 μm and bigger, equivalent to an ISO 9 certified cleanroom. By comparison, an ISO 14644 -1 level 1 certified cleanroom permits no particles in that size range, and just 12 particles for each cubic meter of 0.3 μm and smaller. Semiconductor facilities often get by with level 7 or 5, while level 1 facilities are exceedingly rare. The modern cleanroom

3672-506: The following formula C N = 10 N ( 0.1 D ) 2.08 {\displaystyle {\text{C}}_{\text{N}}=10^{\text{N}}\left({\frac {0.1}{\text{D}}}\right)^{2.08}} Where C N {\displaystyle {\text{C}}_{\text{N}}} is the maximum concentration of particles in a volume of 1m 3 {\displaystyle ^{3}} of airborne particles that are equal to, or larger, than

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3744-475: The generation of airborne particles. Plastic sheets can be used to restrict air turbulence if the cleanroom design is of the laminar airflow type. Air temperature and humidity levels inside a cleanroom are tightly controlled, because they affect the efficiency and means of air filtration. If a particular room requires low enough humidity to make static electricity a concern, it too will be controlled by, e.g., introducing controlled amounts of charged ions into

3816-446: The heavy water, and since light water has a very large cross section for neutron capture, these neutrons are captured very quickly. Gamma rays of roughly 2.2 MeV are produced in this reaction, but because the energy of the photons is less than the detector's energy threshold (meaning they do not trigger the photomultipliers), they are not directly observable. However, when the gamma ray collides with an electron via Compton scattering,

3888-523: The late 1960s, experiments have hinted that neutrinos may have mass. Theoretical models of the Sun predict that neutrinos should be made in large numbers. Neutrino detectors on the Earth have repeatedly seen fewer than the expected number of neutrinos. Because neutrinos come in three varieties (electron, muon, and tau neutrinos), and because solar neutrino detectors have been primarily sensitive only to electron neutrinos,

3960-447: The mine management was willing to make the location available for only incremental costs. The SNO collaboration held its first meeting in 1984. At the time it competed with TRIUMF 's KAON Factory proposal for federal funding, and the wide variety of universities backing SNO quickly led to it being selected for development. The official go-ahead was given in 1990. The experiment observed the light produced by relativistic electrons in

4032-411: The number and size of particles permitted per volume of air. Large numbers like "class 100" or "class 1000" refer to FED-STD-209E , and denote the number of particles of size 0.5 μm or larger permitted per cubic foot of air. The standard also allows interpolation; for example SNOLAB is maintained as a class 2000 cleanroom. A discrete, light-scattering airborne particle counter is used to determine

4104-425: The patient. In another case, severely immunocompromised patients sometimes have to be held in prolonged isolation from their surroundings, for fear of infection. At the extreme, this necessitates a cleanroom environment. The same is the case for patients carrying airborne infectious diseases, only they are handled at negative, not positive pressure. In exobiology when we seek out contact with other planets, there

4176-534: The precision of the original result. Although Super-K had beaten SNO to the punch, having published evidence for neutrino oscillation as early as 1998, the Super-K results were not conclusive and did not specifically deal with solar neutrinos. SNO's results were the first to directly demonstrate oscillations in solar neutrinos. This was important to the standard solar model . In 2007, the Franklin Institute awarded

4248-412: The preferred explanation over the years is that those "missing" neutrinos had changed, or oscillated, into a variety for which the detectors had little or no sensitivity. If a neutrino oscillates , according to the laws of quantum mechanics , then it must have a mass. In 1984, McDonald's collaborator Herb Chen at the University of California at Irvine suggested the advantages of using heavy water as

4320-552: The same rate in both the heavy and light water. The first scientific results of SNO were published on 18 June 2001, and presented the first clear evidence that neutrinos oscillate (i.e. that they can transmute into one another), as they travel from the Sun. This oscillation, in turn, implies that neutrinos have non-zero masses. The total flux of all neutrino flavours measured by SNO agrees well with theoretical predictions. Further measurements carried out by SNO have since confirmed and improved

4392-557: The sampling system. US FED-STD-209E was a United States federal standard. It was officially cancelled by the General Services Administration on November 29, 2001, but is still widely used. Current regulating bodies include ISO, USP 800, US FED STD 209E (previous standard, still used). EU GMP guidelines are more stringent than others, requiring cleanrooms to meet particle counts at operation (during manufacturing process) and at rest (when manufacturing process

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4464-881: The similarities between the requirements of a ventilator and those of particle physics experiments. McDonald led the Canadian team with members from TRIUMF laboratory, CNL Chalk River, SNOLAB and the McDonald Canadian Astroparticle Physics Research Institute after strong positive response from the Directors of these institutions. The design, called the Mechanical Ventilator Milano, is based on the Manley ventilator but uses modern electronics wherever possible. The details, first published on March 23 by about 150 collaborators, were released under

4536-428: The surrounding community . The opposite is done, e.g., in the case of high-level bio-laboratories that handle dangerous bacteria or viruses; those are always held at negative pressure , with the exhaust being passed through high-efficiency filters, and further sterilizing procedures. Both are still cleanrooms because the particulate level inside is maintained within very low limits. Some cleanroom HVAC systems control

4608-416: The technology of the time. McElroy also wrote a four-page article for MicroContamination Journal, wet processing training manuals, and equipment manuals for wet processing and cleanrooms. A cleanroom is a necessity in the manufacturing of semiconductors and rechargeable batteries , the life sciences , and any other field that is highly sensitive to environmental contamination. Cleanrooms can range from

4680-478: The technology, and to be less susceptible to catastrophic failure. With such a wide area of application, not every cleanroom is the same. For example, the rooms utilized in semiconductor manufacturing need not be sterile (i.e., free of uncontrolled microbes), while the ones used in biotechnology usually must be. Vice versa, operating rooms need not be absolutely pure of nanoscale inorganic salts, such as rust , while nanotechnology absolutely requires it. What then

4752-470: The typical flora are primarily those associated with human skin ( Gram-positive cocci ), although microorganisms from other sources such as the environment ( Gram-positive rods ) and water ( Gram-negative rods ) are also detected, although in lower number. Common bacterial genera include Micrococcus , Staphylococcus , Corynebacterium , and Bacillus , and fungal genera include Aspergillus and Penicillium . Cleanrooms are classified according to

4824-401: The very small to the very large. On the one hand, a single-user laboratory can be built to cleanroom standards within several square meters, and on the other, entire manufacturing facilities can be contained within a cleanroom with factory floors covering thousands of square meters. Between the large and the small, there are also modular cleanrooms. They have been argued to lower costs of scaling

4896-457: The vessel was filled with normal water to provide both buoyancy for the vessel and radiation shielding . The heavy water was viewed by approximately 9,600 photomultiplier tubes (PMTs) mounted on a geodesic sphere at a radius of about 850 centimetres (28 ft). The cavity housing the detector was the largest in the world at such a depth, requiring a variety of high-performance rock bolting techniques to prevent rock bursts. The observatory

4968-454: The water created by neutrino interactions. As relativistic electrons travel through a medium, they lose energy producing a cone of blue light through the Cherenkov effect , and it is this light that is directly detected. The SNO detector target consisted of 1,000 tonnes (1,102 short tons ) of heavy water contained in a 6-metre-radius (20 ft) acrylic vessel. The detector cavity outside

5040-526: Was attractive because Atomic Energy of Canada Limited , which maintains large stockpiles of heavy water to support its CANDU reactor power plants, was willing to lend the necessary amount (worth CA$ 330,000,000 at market prices) at no cost. The Creighton Mine in Sudbury is among the deepest in the world and, accordingly, experiences a very small background flux of radiation. It was quickly identified as an ideal place for Chen's proposed experiment to be built, and

5112-499: Was invented by American physicist Willis Whitfield . As an employee of the Sandia National Laboratories , Whitfield created the initial plans for the cleanroom in 1960. Prior to Whitfield's invention, earlier cleanrooms often had problems with particles and unpredictable airflows . Whitfield designed his cleanroom with a constant, highly filtered airflow to flush out impurities. Within a few years of its invention in

5184-531: Was to be a detector facility using 1000 tonnes of heavy water located 6,800 feet (2,100 m) underground in a mine outside Sudbury, Ontario. Chen died of leukemia in November 1987, however. In August 2001, the Sudbury Neutrino Observatory , led by McDonald since 1989, reported observations that directly suggested electron neutrinos from the Sun were oscillating into muon and tau neutrinos. McDonald

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