The back transition and hysteresis effects in DIII-D

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The back transition from H-mode to L-mode has been studied on DIII-D as a part of the investigation of the L-H transition power threshold scaling. Based on a density-dependent scaling for the H-mode power threshold, ITER will require substantial hysteresis in this parameter to remain in H-mode as n{sub e} rises. Defining the hysteresis in terms of the ratio of sustaining to threshold power, P{sub HL}/P{sub LH} may need to be as small as 50% for ITER. Operation of DIII-D at injection powers slightly above the H-mode threshold results in an oscillatory behavior with multiple forward-backward transitions in the course ... continued below

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14 p.

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Thomas, D.M.; Groebner, R.J.; Burrell, K.H.; Osborne, T.H. & Carlstrom, T.N. September 1, 1997.

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Description

The back transition from H-mode to L-mode has been studied on DIII-D as a part of the investigation of the L-H transition power threshold scaling. Based on a density-dependent scaling for the H-mode power threshold, ITER will require substantial hysteresis in this parameter to remain in H-mode as n{sub e} rises. Defining the hysteresis in terms of the ratio of sustaining to threshold power, P{sub HL}/P{sub LH} may need to be as small as 50% for ITER. Operation of DIII-D at injection powers slightly above the H-mode threshold results in an oscillatory behavior with multiple forward-backward transitions in the course of a discharge. These discharges represent a unique system for studying various control parameters that may influence the H{leftrightarrow}L state transition. Careful analysis of the power flow through the edge gives values for the sustaining power which are well below the corresponding threshold powers (P{sub HL}/P{sub LH} = 35--70%), indicating substantial hysteresis can be achieved in this parameter. Studies of other control parameter candidates such as edge temperature during the back transitions are less clear: the amount of hysteresis seen in these parameters, if any, is primarily dependent on the nature (ELMing, ELM-free) of the parent H-state.

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14 p.

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INIS; OSTI as DE98003936

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  • US/Japan workshop on H-mode physics and 6th H-mode workshop, Kloster Seeon (Germany), 22-24 Sep 1997

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  • Other: DE98003936
  • Report No.: GA--A22697
  • Report No.: CONF-9709100--
  • Grant Number: AC03-89ER51114;FG05-88ER53266
  • Office of Scientific & Technical Information Report Number: 639746
  • Archival Resource Key: ark:/67531/metadc696419

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • September 1, 1997

Added to The UNT Digital Library

  • Aug. 14, 2015, 8:43 a.m.

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  • Aug. 1, 2016, 6:33 p.m.

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Thomas, D.M.; Groebner, R.J.; Burrell, K.H.; Osborne, T.H. & Carlstrom, T.N. The back transition and hysteresis effects in DIII-D, article, September 1, 1997; San Diego, California. (digital.library.unt.edu/ark:/67531/metadc696419/: accessed October 21, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.