{"id":768,"date":"2017-03-20T21:04:54","date_gmt":"2017-03-20T21:04:54","guid":{"rendered":"http:\/\/www.btitargetry.com\/?page_id=768"},"modified":"2017-03-27T14:51:39","modified_gmt":"2017-03-27T14:51:39","slug":"visualization-target-wttc14","status":"publish","type":"page","link":"https:\/\/www.btitargetry.com\/?page_id=768","title":{"rendered":"Visualization Target (WTTC14)"},"content":{"rendered":"

Visual Observation of Boiling in High Power Liquid Target<\/span><\/strong><\/p>\n

J. Peeplesa,1<\/sup>, M. Stokelya<\/sup>, M. Poormana<\/sup>, M. Magerlb<\/sup>, B. Wielanda<\/sup><\/p>\n

a<\/sup><\/em>BTI Targetry LLC, 1939 Evans Rd. Cary, NC, USA<\/em><\/p>\n

b<\/sup><\/em>IBA Molecular, 801 Forestwood Dr. Romeoville, IL, USA<\/em><\/p>\n

A top pressurized, batch style, 3.15 mL total volume water target with transparent viewing windows was operated on an IBA 18\/9 cyclotron at 18 MeV proton energy and beam power up to 1.1 kW.\u00a0 Video recordings documented bubble formation and transport, and blue light from de-excitation of water molecules produced images of proton beam stopping geometry including location of the Bragg peak.<\/p>\n

Background and Motivation<\/b><\/p>\n

Prior publications by other researchers used visualization targets to document measurements at disparate pressures, power levels, and fill volumes.\u00a0 This target features realistic dimensions and was operated at high pressures and beam currents consistent with recently deployed targets used for routine production.<\/p>\n

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Theory and Lighting Effects<\/b><\/p>\n

During irradiation, the proton beam excites the water molecules, producing visible blue light emissions during de-excitation.\u00a0 These light emissions can be recorded using a video camera in dark ambient conditions and used to observe the position of the Bragg peak and detect beam penetration.\u00a0 With good ambient lighting, the width of the Bragg peak and natural circulation effects are clearly visible.\u00a0 When a strong backlight is employed, it is possible to see and record bubble formation and transport in the target chamber.<\/p>\n

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Visualization Target<\/b><\/p>\n

The visualization target featured an aluminum body with a 0.005\u201d integral aluminum window and two viewing windows made of optically clear sapphire (Al2O3).\u00a0 The chamber dimensions were 14 x 15 x 15 mm, for a 3.15 mL maximum volume.\u00a0 Due to the excellent physical and thermal properties of the sapphire viewing windows and the use of well-optimized water cooling, the target can be operated at typical production beam powers and operating pressures with a realistic chamber volume.<\/p>\n

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Simulation of Visualization Target<\/b><\/p>\n

Thermal performance of batch production targets was previously correlated to average void to develop performance models (Peeples 2011).\u00a0 The visualization experimental results can be compared to simulations of the visualization target for the same current and pressure.<\/p>\n

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Experimental Results<\/b><\/p>\n

The target was operated as high as 1.1 kW on an 18\/9 cyclotron with a fill volume\u00a0 of 2.5 mL.\u00a0 Beam collimation to 10 mm diameter, use of an extension on the beam port, and cyclotron tuning resulted in a maximum available current on target of 65\u00b5A.\u00a0 Stable natural convection, bubble diameter and transport as a function of operating pressure, and particle range for a variety of currents and pressures were observed and recorded.<\/p>\n

Stable Natural Convection<\/em><\/strong><\/p>\n

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19\u03bcA, 215psi \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 \u00a0 19\u03bcA, 215psi<\/span><\/p>\n

Beam Penetration due to Under Fill<\/em><\/strong><\/p>\n

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Effect of Pressure on Bubble Diameter<\/em><\/strong><\/p>\n

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Disruption of Helium due to Pressure Oscillations<\/em><\/strong><\/p>\n

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