Portable X-ray Betatron

Transcription

1 2.5MeV to 50MeV Quotable Portable X-ray Betatron 6 MeV - PXB MeV - PXB 7.5 Compact, powerful, mobile, versatile Output energy selectable up to 7.5 MeV Operates from single phase AC supply Automatic exposure control facility Excellent sensitivity and resolution Penetrates 300mm steel, 1m concrete

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3 The JME 6MeV Portable Betatron the structures we depend upon must perform their intended functions with the absolute minimum risk of failure... In today's world the structures we depend upon must perform their intended functions with the absolute minimum risk of failure in service. Serious injury or long-lasting damage to the environment, not always limited to the immediate vicinity of the structure, can result from deterioration in the strength of industrial components and installations such as:- * Containers, pipelines and flow control valves for high pressure or hazardous substances. * Ships hulls and marine components * Engineering components and castings * Conventional and nuclear power stations * Steel or reinforced concrete structures including bridges, public facilities and high-rise buildings * Military hardware, propellants and munitions It is essential that the major load-bearing or pressureretaining components of such structures are proved to be free from weaknesses or defects at the time of construction. In addition, routine inspection should be carried out to monitor and correct any deterioration well before failure could possibly occur. Of the methods devised for analysing the thick metal or concrete sections used in major structures, only radiography can give a direct and exact hard-copy profile picture of the interior geometry and condition of such sections. This is achieved by passing an X-ray beam through the object and recording the internal profile as a shadow picture on a sheet of film, or by means of a radiation sensor array and video system. Any cracks, cavities, defects or missing components will transmit more radiation than the adjacent sound material, and will therefore show up on the picture. Although this inspection method has been used for many decades, the problem for thick sections, above about 80mm for steel or 250mm for concrete, has always been the generation of an X-ray beam with enough energy to give a satisfactory picture from equipment light and compact enough to be carried easily to the structure and to fit into the often confined spaces around it. A typical site radiography system can weigh many hundreds of kilograms and produces an X-ray energy up to about 450 thousand volts. The JME Betatron, with a total system weight of 190 kg produces a remarkable energy of 6 million volts. This energy is usually only generated by large, heavy and very expensive X-ray generators permanently installed in special inspection laboratories, or for which a large vehicle, handling crane and special cooling equipment are essential. The JME Betatron allows the internal geometry and condition of steel sections up to 300mm thick and concrete sections of 1 metre or more to be rapidly investigated in-situ. The JME Betatron can be carried in an ordinary car and takes its electrical power from a light-duty single-phase outlet or small AC generator supplying 110/240 volts. The X-ray emitter measures only 60 x 40 x 23cm and weighs only 90kg. In addition, the conversion of electrical to X-ray energy through the JME Betatron's pulsed magnetic circuit and circular vacuum accelerator tube is many times more efficient so even during long continuous periods of use it does not require a complex liquid cooling system but uses small integral ventilator fans. With its directional output beam and very low scattered radiation levels in all other directions, the JME Betatron presents a much smaller radiation hazard during on-site use than other types of X-ray source. Prior to the development of this compact highenergy electrical X-ray machine, radioactive isotopes were often used for the inspection of thick sections. Isotopes suffer from the disadvantages of lower energy (resulting in reduced object penetration), poorcontrast radiographs causing defect recognition difficulties, and steadily decreasing output necessitating regular costly replenishment. In particular, they are a permanent safety hazard during transportation and storage as well as during use because, unlike the JME Betatron, they can never be switched off. To sum up, the JME Betatron, a product of recent UK electronic design innovation, is intended to play a key role in supporting mankind's increasing awareness of the potential hazards to people and the environment through necessary use of industrial installations and structures. The JME Betatron is already being used by Britain's National Non- Destructive Testing Centre at Harwell, and Nuclear Electric, the UK power generating Company. Many other industries, including engineering, shipbuilding, military and civil construction concerns are showing keen interest. At one end of its range of applications is current research on computerdisplayed three-dimensional radiography, or tomography. At the other extreme a precise picture of the layout and condition of steel reinforcement bars in concrete structures or buildings, or a scan of the contents of sealed containers at remote locations, or detailed in-situ analysis of critical weld sections, may be achieved within a few minutes.

4 Donald W. Kerst with the world s first Betatron (c. 1939) Development History The concept of the Betatron Electron Accelerator was devised over 50 years ago, with the first systems being developed as research tools for high energy physics investigations. This early equipment was heavy, bulky, complex and immobile, and was unsuitable for general radiographic inspection purposes. Subsequent decades saw steady development of the Betatron for industrial NDT use, as engineering structures gradually became larger, the loading and therefore thickness of their critical components increased, and inspection specifications became ever more severe. ogy, and timing and control circuitry, have resulted in further substantial reductions in the Betatron s size and complexity. Consequently, in its present compact, reliable and highly efficient form, the Betatron has become an invaluable and fully mobile tool for a wide range of NDT applications, including both traditional film radiogra- in its present compact, reliable and highly efficient form, the Betatron has become an invaluable and fully mobile tool... World s first medical Betatron (c. 1942) Operating Principle To accelerate electrons to the very high energy required for 6 MeV X-rays, the Betatron utilises a ring-shaped (toroidal) glass vacuum tube sandwiched between the specially shaped pole pieces of an electromagnet. Synchronised electron pulses from a heated filament within the tube are injected into a circular equilibrium orbit, and are accelerated during the first quarter of each magnetic cycle while the field is rising from zero to maximum. The pulse repetition rate, and applied electro-magnet voltage frequency, are 4 times the ac supply frequency, i.e. 200 or 240 per second from 50 or 60 Hz supply respectively. After about a million revolutions of each electron pulse, occurring within a few milliseconds (during which time the electron velocity almost reaches that of light), a precisely synchronised expansion signal is automatically applied to the electro-magnet. The fast moving electron pulse then spirals outwards to collide at grazing incidence with the edge of a small tantalum target mounted within the vacuum tube. This sudden deceleration of high velocity electrons produces a continuous stream of X-ray pulses, outwards along a tangent from the target position. The elliptical X-ay beam, with beam-spread angle of 25 Now, recent advances in electro-magnet design, solid state electronic component technolto 30, emerges from a rectangular window in the side of the accelerator housing after traversing a built in dose rate meter with readout on the control panel. The beam-spread covers a 430 x 355 mm (17 x 14 ) sheet of X-ray film placed at 1 metre from the target. The broad band X-ray spectrum, extending from about 500 kv to a peak energy of 6 MeV, produces images of excellent contrast and sensitivity. The very small focal spot (only 0.2 x 1 mm) permits extremely high resolution. Conversion of electron energy to X-rays in the tantalum target is very efficient, so that water cooling of the X-ray tube is not required, nor is any run-up or

5 6MeV Portable X-Ray Betatron for High Definition Radiography of Thick or Dense Sections The JME Betatron is based on a very compact and easily operated circular X-ray accelerator. It combines high reliability with mobility and ease of shielding during in-situ examination of large objects or fixed structures for which permanent radiographic exposure chambers cannot be used. The complete system (comprising accelerator, power converter, control panel, automatic exposure unit, radiation alarm and connection cables) weighs only 190 kg. The JME Betatron operates from an ordinary 3 kilowatt single phase electrical mains supply, or from a mobile generator of about 20 KVA rating. Radiation shielding during open air on onsite use, such as inspection of large pressure vessels or reinforced concrete civil engineering structures, is much easier than with other high energy X- ray systems, because of the modest output dose of 3-5 Rads per minute at 1 metre Basic Description The PXB-6 is a compact, portable, reliable, simple to operate and simple to maintain system, for the generation of high energy X- rays for radiographic inspection of thick or dense materials, up to about 280 mm (11 ) steel or 1 metre (40 ) concrete. The complete system comprises of X-ray accelerator unit, power converter unit, remote control panel, remote (film slide) dosemeter unit, automatic safety alarm beacon/siren and laser alignment device. The system draws electrical power from a single phase AC mains supply or from a portable electrical generator (see specification). No other services are required. in the main beam direction and average back-scatter only 3% in other directions. But penetrating power is equal to high dose linear accelerators, with 1/2 value layers for steel and concrete of about 28 and 100 mm respectively at 6 MeV. The high durability tantalum X-ray target produces very little heat so no costly, cumbersome water cooling system is needed. Radiographic definition is high because the focal spot size is only 0.2 x 1.0 mm, and direct enlargements are possible using the Microfocus principle. Recent tests have shown that excellent radiographic sensitivity and contrast may be achieved using Fluoro Metallic intensifying screens. These FM screens are about 5 times faster than plain lead screens. For film density 2.5, with very fine grain film such as Kodak AX for example, necessary transmitted radiation dose at 6 MeV is about 2.5 Rads with plain lead The radiation dose, received by an X-ray film is monitored by a small ionisation chamber dosemeter unit, so that exposure levels may be automatically pre-set and timed. Audible and visible radiation warning signals are provided. A siren sounds for a specified period following actuation of the X-RAY ON control, followed by a flashing beacon while radiation is actually being emitted. Existing interlock and warning circuits may also be directly connected into the Betatron system controls. The combined weight and screens but only 0.5 Rad for FM screens. The PXB-6 Portable X-Ray Betatron thus gives radiographic quality and exposure times which compare favourably with much larger, heavier, more complex and more expensive accelerators requiring water cooling, a heavy duty 3 phase electrical power supply and a large vehicle and hoist for transportation and handling. volume of the entire system (including inter-connecting cables) are respectively 190 kg (420 lb) and 0.25 cubic metre (9 cu.ft.). The X-ray accelerator unit by itself weighs 90 kg (200 lb) with a volume of 0.06 cu.m. (2 cu.ft.). The Betatron is based on a very compact, easily operated circular X-ray accelerator....combines high reliability with mobility and ease of shielding during insitu examination of large objects... The complete system weighs only 190 kg (420 lb).

6 Applications Investigation of the packing characteristics of solid propellants. many inspection projects have been successfully accomplished for which no alternative methods or equipment are available... The JME Betatron has been extensively used by leading UK engineering and NDT organisations since Its reliability, mobility, simplicity of operation, ease of maintenance, wide range of application and relatively low cost are well established. Many radiographic inspection projects have been successfully accomplished for which no comparable alternative methods or equipment are available. Typical applications include the following: Critical weld inspection during fabrication of large stainless steel pressure vessels for nuclear power stations. Very high radiographic sensitivity (typically 0.5%) is achieved with the JME Betatron, using very fine grain film and lead intensifying screens. Very small inclusions or defects are clearly detected at each stage of construction, without having to move the pressure vessel from the fabrication shop during radiography. Examination of major engineering components such as large valves, pressure vessels, motors, machinery units and load-bearing structural sections in industries such as construction, power generation, aviation, mining, petrochemicals, shipbuilding, transportation, etc. Investigation of the packing characteristics of solid propellant in satellite launch rocket motors. Inspecting reinforced concrete structural components such as bridge beams and suspension ties, and slabs and stanchions for high-rise and public buildings. Such tests have the objective of establishing the presence and exact location of steel reinforcement bars or mesh, and assessing structural safety by revealing possible corrosion of reinforcement and consequent cracking of the concrete matrix. Identification of the contents of storage drums containing low-level radioactive waste materials embedded in concrete. The JME Betatron is ideally suited for in-situ inspection of any heavy fixed structure or component which cannot be dismantled for transportation to a specialised radiographic exposure facility. Because of its very low backscattered radiation levels, the JME Betatron may be safely used with small portable shielding panels at locations where permanently installed radiaition shielding is not available. Recent experience has shown that the JME Betatron is ideally suited for use with the latest real time equipment utilising image detection, enhancement and recording. Such techniques have a valuable applica- Examination of engineering components such as large valves, pressure vessels, machinery units, etc. Construction and Safety The JME Betatron is designed and manufactured to very high standards of electrical and radiation safety and reliability, in compliance with the requirements of the British Nuclear Electricity Industry and the UK National Non- Destructive Testing Centre. Safety inter-locks and component quality are based on relevant British Standards. The JME Betatron is intended to produce ionising radiation in the form of X-rays (for the purpose of radiographic inspection) by means of electron acceleration within a sealed vacuum tube enclosed by an electromagnet assembly. It does not contain or make use of radioactive material in any form. It is completely inert and safe, and unable to produce any radiation whatsoever, when the external electrical supply is switched off or disconnected. Thus no restriction or special documentation applies to its storage and transportation. Although the JME Betatron produces X-rays of energy 6 MeV, this energy is attained by multiple orbits of the electron pulse, with only a small energy increment during each orbit. The maximum electrical voltage present outside the sealed injection/acceleration unit is the electromagnet supply of about 1 kv. It is essential that the JME Betatron is operated and serviced only by appropriately experienced, supervised and monitored personnel, in strict accordance with applicable local and national ionising radiation

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9 Technical Specifications Peak energy of broad-beam X-ray emission MeV 6 Maximum effective width of energy spectrum MeV Peak energy selection levels MeV Radiation dose rate in air at 1 metre (6 MeV) Rads/min cgy/min Mean X-ray beam spread to 80% dose rate contour degrees 30 Radiation field coverage at 1 metre (nominal) mm 450 x 400 Radiation pulse duration microseconds 5 Pulse repetition rate per second 200 Total radiation on time per second (0.1%) milliseconds 1 Electrical supply (50/60 Hz, single phase) V Overall power consumption (mains supply use only) kw 2.8 Heat dissipation in accelerator electromagnet (approx) kw 2 Cooling of power unit and electromagnet Airflow fans Heat dissipation in X-ray target (approx) W 10 Cooling of X-ray source target Pre-warming or seasoning of X-ray tube Not required Not required Conversion efficiency of electron beam kinetic energy into X-ray energy (approx) % 40 X-ray source target material Tantalum (Ta) Effective size of X-ray source focal spot mm 0.2 x 1.0 Radiographic sensitivity (optimum) % down to 0.4 X-ray duty cycle at ambient temperature <20ºC % 100 Ambient environmental temperature range ºC -20 to +40 Half Value Layer - Steel mm (in) 28 (1.1) Recommended thickness range - Steel mm (in) (2-11) Half Value Layer - Structural Concrete mm (in) 104 (4.1) Recommended thickness range - Concrete mm (in) (8-39) Half Value Layer - Lead mm (in) 16 (0.63) Equipment module dimensions: X-ray accelerator unit Power converter unit Control panel Equipment module weights: X-ray accelerator unit Power converter unit Control panel Set of 5 interconnecting cables Total system weight (with accelerator handling frame, remote auto dosemeter and radiation alarm siren/beacon) Standard interconnection cable lengths: Power unit to electrical supply Power unit to accelerator (2 cables) Power unit to control panel Power unit to remote auto dosemeter Power unit to alarm siren/beacon cm (in) 60 x 40 x 23 (23 x 16 x 9) 59 x 38 x 36 (23 x 15 x 14) 36 x 32 x 19 (14 x 14½ x 7½) kg (lb) 90 (200) 60 (121) 7 (15) 23 (50) kg (lb) 190 (407) m (ft) 5 (16) 9 (30) 15 (50) 15 (50) 5 (16) Automatic pre-set exposure dose ranges R 0-2½ and 0-10 Recommended electrical generator rating (must be suitable smooth supply) suggest Aggreko 30kVA unit kva 30

10 2.5MeV to 50MeV Quotable Portable X-ray Betatron 6 MeV - PXB MeV - PXB 7.5 Compact, powerful, mobile, versatile Output energy selectable up to 7.5 MeV Operates from single phase AC supply Automatic exposure control facility Excellent sensitivity and resolution Penetrates 300mm steel, 1m concrete

11 Portable X-ray Betatron 6 MeV - PXB MeV - PXB 7.5 General Information The JME Portable Betatron is a compact circular electron accelerator producing a high energy directional X-ray beam. Containing no moving parts except small airflow fans, and no circulating liquids, the Betatron is easy to assemble, operate and maintain, and is far less costly than other NDT accelerators such as Linacs. Radiation levels outside the main beam are low, so safe working distances are moderate. After demarcation of dose rate boundaries, the Betatron may be used at external sites or in fabrication shops with little or no additional shielding. The Betatron produces radiographs of very high contrast, sensitivity and resolution, meeting the tightest inspection standards. It replaces Cobalt isotope gamma sources, which may not give acceptable quality and require costly periodic replenishment. Applications High quality radiographic inspection of: Large forgings, castings, valves, beams Heavy engineering products, ships hulls Pressure vessels, engine blocks, billets Thick welds, dense metals, composites Military hardware, munitions, propellants Reinforced concrete buildings, bridges At the following locations: Engineering works, shipyards, steelworks Conventional and nuclear power stations Civil engineering construction sites Non-Destructive testing establishments Materials and structures research centres Features Penetrates 300mm steel or 1 metre concrete Only requires a single phase AC supply Reliable solid state electronic components Tiny focal spot provides superb resolution Automatic exposure dose timing facility Backscatter very low for personnel safety Low heat output (water cooling not needed) Easy to transport, operate and maintain Technical Specifications PXB 6 PXB 7.5 X-ray output energy selector 2 to 6 MeV 2 to 7.5 MeV Dose rate at 1m (air) 3R per minute 5R per minute Focal Spot Size 0.2 x 1.0 mm 0.3 x 1.6 mm Duty Cycle at 20 C (per hour) 100% 75% Radiation beam spread angle 26 degrees 22 degrees Radiographic sensitivity Down to 0.5% Typically 1% AC power input 110/240V 50/60Hz 115/220V 50/60Hz Dimensions and weight Accelerator Power converter 60 x 40 x 23 cm 90kg 59 x 38 x 36 cm 60kg 70 x 43 x 35 cm 56 x 48 x 38 cm Control panel 36 x 32 x 19 cm 7kg 20 x 13 x 4 cm Total system weight 190 kg 210 kg Technical specification may change in accordance with our policy of continuous product development JME Ltd Electron House, Old Nelson Street, Lowestoft, Suffolk, NR32 1EQ, U.K. Tel: +44 (0) Fax: +44 (0) info@jme.co.uk

12 JME Ltd Electron House Old Nelson Street Lowestoft Suffolk NR32 1EQ Tel: +44 (0) Fax: +44 (0)