1. A Method For Efficient Temperature Measurement of NDCX-II Ion Source
Kavous Mazaheri1, Steven M. Lidia2, Pavel Ni2
1Pinole Valley High School, 2Lawrence Berkeley National Laboratory
ABSTRACT
METHODS
CONCLUSION
NDCX-II is an induction linear accelerator that accelerates a lithium ion beam up to 3 MeV. The NDCX-II lithium ion source is heated up to 1500K and its temperature is monitored during machine operation. Currently the temperature of the source is measured manually with a single channel handheld pyrometer. This method has several disadvantages, including the need to break down a beam line for a clear sight of the source and manual temperature measurement by a person. In this project an automated pyrometer system was developed to measure temperature continuously without breaking the beam line and avoiding the safety hazard of manual measurement. A relay lens system, aligned at a 45 degree angle with respect to the source, collects thermal emission at 650nm. Collected light is modulated with a mechanical chopper and detected with an amplified silicon photodiode. The automated pyrometer is cross-calibrated with the manual handheld pyrometer. The voltage from the diode is digitized and used in Labview for temperature determination using a pre-determined calibration coefficient and the Planck’s formula.
The relay lens takes the image of the source from the optical system, which is aligned to infinity, and make it available to the second optical system. A mechanical chopper with frequency of 200 Hz is positioned in front of a detector (photodiode) which is connected to an oscilloscope.
A functional relay lens system was developed to be used for automated temperature measurement of the NDCX-II. The system seemed to be flawless (squared signal) without the filter; however, the signals became flat after the filter was placed in, and cross calibration was not successful. It is recommended to check the signal for all settings of the detector to determine the optimum setting. The lens must also be positioned properly. If these steps solve the problem, then cross-calibration is attempted again. After successful cross-calibration with the manual handheld pyrometer, the voltage (δV) from the detector is digitized and used in Labview for temperature determination using a pre-determined calibration coefficient and the Planck’s formula.
Injector cross section, showing the position of the source and the window
First optical system aligned with source
Source
Figure 1
Figure 2
INTRODUCTION
ACKNOWLEDGEMENTS
The Heavy Ion Fusion Science Virtual National Laboratory (HIFS-VNL) is applying intense ion beams as drivers for basic studies of warm dense matter (WDM) physics in uniformly heated foils driven by ions near the Bragg peak energy, and is studying their ultimate application for inertial fusion energy. The NDCX-II is the primary tool utilized for this research.
Many thanks to my mentors: Dr. Steven Lidia and Dr.Pavel Ni at Lawrence Berkeley National Laboratory (LBNL) for providing the opportunity and guidance for the project. Also, I would like to extend my appreciation to Dr. Joe Kwan, Takeshi Katayanagi and Mrs. Lynn Heimbucher of the Accelerator and Fusion Research Division for providing a superb and welcoming environment for me. Of course, this awesome experience could not have been possible without the support of the following individuals who made this program a success and enabled me to have such an amazing experience: Dr. Susan Brady, Mary Connolly, the entire Center for Science and Engineering Education staff; Sue Kahn, Pinole Valley High School; and Stephanie Ruzicka, peer coach for Industry Initiatives for Science and Math Education. A special thank to Jin-Young Jung, LBNL Engineering; Kieran Murphy (SULI); and Jonathan Wong, Chinese University of Hong Kong.
Second optical system with detector, chopper, and converging lens
Manual temperature measurement using a handheld pyrometer
RESULTS .
Figure 3
The signal emerging from the detector
as shown on oscilloscope. The lower boundary indicates that the chopper is completely blocking the source, but not the noise. The upper boundary indicates that the detector is unblocked.
Figure 4
Handheld temperature measurement cross calibrated with delta V
NDCX-II