Preliminary Study Of Fast Ion Loss Diagnostic(FILD)on EAST

This article introduces the fast ion loss diagnosis system and the preliminary application on EAST device in detail.In recent years,EAST has made great progress in plasma heating,plasma magnetic control,plasma diagnostics and physical research,especially in the future ITER’s goal of achieving high power long pulse steady-state plasma,and access to world attention achievements.EAST has developed a variety of high-power auxiliary heating systems,including lower hybrid current drive system,ion cyclotron heating system,electron cyclotron heating system,and neutral beam injection system,with a total heating and current drive power more than 20MW.These auxiliary heating systems provide a rich fast ion source,help to achieve steady-state high-performance plasma.However,due to the presence of the first orbital loss and instability,it is possible to cause a large loss of fast ions.The loss of these fast ions,on the one hand will reduce the auxiliary heating efficiency,affecting the combustion of plasma performance,on the other hand will cause damage to the first wall of the device.Therefore,the establishment of fast ion loss diagnosis on EAST and the study of fast ion loss behavior are very critical and necessary.This paper focuses on the main components of the new FILD system,including four parts:fast ion loss detection system,drive system,imaging optical system and data acquisition system.The scintillator-based fast ion loss probe is an important diagnostic device for measuring fast ion loss in the tokamak device and is mounted on the plane of the J port in EAST.The lost fast ions pass through the front and rear slits of the collimation system of the detection system and eventually strike the scintillator screen on the detection system.The use of the drive system can not only make the detection system moving rapidly,but also the detector can change direction in the positive and negative field discharge,to ensure that the detection system can quickly change the direction of the front aperture and collect the experimental data timely.In order to amplify and collect the fast ion loss signal detected on the scintillator in the probe,the imaging optical path system is designed in the fast ion loss diagnosis system and the light on the scintillator is collected on two sets of data acquisition systems.A part of the light is transmitted to the CCD high-speed camera(Phantom V2010)through the beam splitter to record the fluorescence image on the scintillator screen,and the pitch angle and the radius of rotation of the fast ions can be obtained at any frame.Another part of the light is transmitted to the 25-channel PMT data acquisition system,which can acquire fast ion loss signal.It has the unique advantages of setting the magnification of each channel independently,each channel can be checked individually and can remotely control during the experiment discharge.In the development of diagnostic system,verified the reliability of the diagnostic system and study the fast ion loss basic behaviors.Fast ion loss behaviors have been observed in different discharge conditions.In the case of neutral beam implantation,the behavior of fast ion loss in the reverse direction is observed when the Plasma disruption happens;runaway electrons and fast electrons will increase the background of the signals for fast ion loss;in ICRF heating discharges,lost fast ions have also been detected;the fast ion loss signal will change with the ELMs in the H-mode discharge;resonant magnetic perturbation and supersonic molecule beam injection can enhance the loss of fast ions.