ECRIS-2014 - Table of Session: MOOBMH (M2)

Paper

Title

Page

Periodic Beam Burrent Oscillations Driven By Electron Cyclotron Instabilities In ECRIS Plasmas

5

O.A. Tarvainen, T. Kalvas, H. A. Koivisto, J.P.O. Komppula, R.J. Kronholm, J.P. Laulainen
JYFL, Jyväskylä, Finland
I. Izotov, D. Mansfeld, V. Skalyga
IAP/RAS, Nizhny Novgorod, Russia
V. Toivanen
CERN, Geneva, Switzerland

Experimental observation of cyclotron instabilities in electron cyclotron resonance ion source plasma operated in cw-mode is reported. The instabilities are associated with strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents. The instabilities are shown to restrict the parameter space available for the optimization of high charge state ion currents.

Slides MOOBMH01 [2.020 MB]

MOOBMH02

Emittance Measurements For RIKEN 28 GHz SC-ECRIS

10

Y. Higurashi, T. Nakagawa, J. Ohnishi, K. Ozeki
RIKEN Nishina Center, Wako, Japan

In 2013, the intense beams of highly charged uranium ion (180euA of U³⁵⁺, 230euA of U³³⁺) were extracted from RIKEN SC-ECRIS. Following the success, intense beam of U³⁵⁺ ions was used for the RIBF experiment for 24 days without break. It is obvious that production of high-quality beam (smaller emittacne and good stability etc) is also important for RIKEN radio isotope beam factory (RIBF) project. For this reason, in 2014, we systematically measured the emittance and beam intensity of the highly charged uranium ions under various conditions (magnetic field configuration, extracted beam intensity, beam stability etc) to search the optimum condition. In these experiments, we observed that the emittnce size is strongly dependent on the magnetic field configuration, especially Bext. In this contribution, we present the effect of the various parameters (magnetic field configuration, extracted beam intensity, beam stability etc) of the SC-ECRIS on the beam intensity and emittance. We also discuss its mechanism in detail.

Slides MOOBMH02 [2.472 MB]

MOOBMH03

Frequency Tuning Effect On The Bremsstrahlung Spectra, Beam Intensity And Shape In An ECR Ion Source

15

G.O. Rodrigues, D. Kanjilal, N. Kumar, K. Mal, Y. Mathur
IUAC, New Delhi, India
A. Roy
VECC, Kolkata, India

The effect of the frequency tuning on bremsstrahlung spectra, beam intensity and shape in the 10 GHz, Nanogan ECR ion source have been investigated. The main aim of this work was to study the effect on a lower frequency type of ECR source where the separation between various modes in the cavity is much larger. The warm and cold components of the electrons were observed to be directly correlated with the beam intensity enhancement in the case of Ar⁹⁺ but not so for O⁵⁺. However, the warm electron component was much smaller than the cold component. The beam shapes of O⁵⁺ measured as a function of frequency showed a strong variation without hollow beam formation. Due to the use of an octupole magnetic structure in the Nanogan ECR source, the quadrupolar structure of the ECR surface is modified with the frequency tuning. In general, we have observed a strong absorption of microwave power at various frequencies whenever the reflection co-efficient showed a minimum value and the effect was seen stronger for the higher charge states. Details of the measurements carried out on the bremsstrahlung spectra, beam intensity and shape are presented together with the results of simulations.
* Effect of frequency tuning on bremsstrahlung spectra, beam intensity, and shape in the 10 GHz NANOGAN electron cyclotron resonance ion source, Rev. Sci.Instrum. 85,02A944 (2014)

Slides MOOBMH03 [23.075 MB]

MOOBMH04

Emission Spectroscopy Diagnostic of Plasma Inside 2.45 GHz ECR Ion Source at PKU

20

Y. Xu, J. Chen, J.E. Chen, Z.Y. Guo, S.X. Peng, H.T. Ren, J.F. Zhang, T. Zhang, J. Zhao
PKU, Beijing, People's Republic of China
A.L. Zhang
Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China

Funding: This work is supported by the National Science Foundation of China (Grant Nos. 11175009 and 91126004).
The 2.45 GHz permanent magnet electron cyclotron resonance ion source (PMECR) at Peking University (PKU) can produce 100 mA H⁺, 40 mA H²⁺ and 20 mA H³⁺ under different conditions, but the physics processes and plasma characteristics within the discharge chamber are not very clear until now. Langmuir probe, laser detachment, absorption spectroscopy and optical emission spectroscopy are common approaches for diagnosing the plasma. Among those methods, optical emission spectroscopy is a simple in situ one without disturbing the plasma. To better understand the plasma producing processes, a new ion source with transparent quartz discharge chamber was designed at PKU so that plasma diagnostic can be performed through directly detecting the light generated within ECR zone by fiber optics. Collisional radiative (CR) model is utilized to calculate plasma parameters like electron density ne and electron temperature Te for non-equilibrium plasma in ECR ion source. The spectroscopy diagnosis platform has been constructed, and preliminary results will be presented in this paper.
*Author to whom correspondence should be addressed. Electronic mail:
sxpeng@pku.edu.cn.

Slides MOOBMH04 [2.330 MB]

Paper	Title	Page
MOOBMH01	Periodic Beam Burrent Oscillations Driven By Electron Cyclotron Instabilities In ECRIS Plasmas	5
	O.A. Tarvainen, T. Kalvas, H. A. Koivisto, J.P.O. Komppula, R.J. Kronholm, J.P. Laulainen JYFL, Jyväskylä, Finland I. Izotov, D. Mansfeld, V. Skalyga IAP/RAS, Nizhny Novgorod, Russia V. Toivanen CERN, Geneva, Switzerland
	Experimental observation of cyclotron instabilities in electron cyclotron resonance ion source plasma operated in cw-mode is reported. The instabilities are associated with strong microwave emission and a burst of energetic electrons escaping the plasma, and explain the periodic oscillations of the extracted beam currents. The instabilities are shown to restrict the parameter space available for the optimization of high charge state ion currents.
	Slides MOOBMH01 [2.020 MB]

MOOBMH02	Emittance Measurements For RIKEN 28 GHz SC-ECRIS	10
	Y. Higurashi, T. Nakagawa, J. Ohnishi, K. Ozeki RIKEN Nishina Center, Wako, Japan
	In 2013, the intense beams of highly charged uranium ion (180euA of U³⁵⁺, 230euA of U³³⁺) were extracted from RIKEN SC-ECRIS. Following the success, intense beam of U³⁵⁺ ions was used for the RIBF experiment for 24 days without break. It is obvious that production of high-quality beam (smaller emittacne and good stability etc) is also important for RIKEN radio isotope beam factory (RIBF) project. For this reason, in 2014, we systematically measured the emittance and beam intensity of the highly charged uranium ions under various conditions (magnetic field configuration, extracted beam intensity, beam stability etc) to search the optimum condition. In these experiments, we observed that the emittnce size is strongly dependent on the magnetic field configuration, especially Bext. In this contribution, we present the effect of the various parameters (magnetic field configuration, extracted beam intensity, beam stability etc) of the SC-ECRIS on the beam intensity and emittance. We also discuss its mechanism in detail.
	Slides MOOBMH02 [2.472 MB]

MOOBMH03	Frequency Tuning Effect On The Bremsstrahlung Spectra, Beam Intensity And Shape In An ECR Ion Source	15
	G.O. Rodrigues, D. Kanjilal, N. Kumar, K. Mal, Y. Mathur IUAC, New Delhi, India A. Roy VECC, Kolkata, India
	The effect of the frequency tuning on bremsstrahlung spectra, beam intensity and shape in the 10 GHz, Nanogan ECR ion source have been investigated. The main aim of this work was to study the effect on a lower frequency type of ECR source where the separation between various modes in the cavity is much larger. The warm and cold components of the electrons were observed to be directly correlated with the beam intensity enhancement in the case of Ar⁹⁺ but not so for O⁵⁺. However, the warm electron component was much smaller than the cold component. The beam shapes of O⁵⁺ measured as a function of frequency showed a strong variation without hollow beam formation. Due to the use of an octupole magnetic structure in the Nanogan ECR source, the quadrupolar structure of the ECR surface is modified with the frequency tuning. In general, we have observed a strong absorption of microwave power at various frequencies whenever the reflection co-efficient showed a minimum value and the effect was seen stronger for the higher charge states. Details of the measurements carried out on the bremsstrahlung spectra, beam intensity and shape are presented together with the results of simulations. * Effect of frequency tuning on bremsstrahlung spectra, beam intensity, and shape in the 10 GHz NANOGAN electron cyclotron resonance ion source, Rev. Sci.Instrum. 85,02A944 (2014)
	Slides MOOBMH03 [23.075 MB]

MOOBMH04	Emission Spectroscopy Diagnostic of Plasma Inside 2.45 GHz ECR Ion Source at PKU	20
	Y. Xu, J. Chen, J.E. Chen, Z.Y. Guo, S.X. Peng, H.T. Ren, J.F. Zhang, T. Zhang, J. Zhao PKU, Beijing, People's Republic of China A.L. Zhang Graduate University, Chinese Academy of Sciences, Beijing, People's Republic of China
	Funding: This work is supported by the National Science Foundation of China (Grant Nos. 11175009 and 91126004). The 2.45 GHz permanent magnet electron cyclotron resonance ion source (PMECR) at Peking University (PKU) can produce 100 mA H⁺, 40 mA H²⁺ and 20 mA H³⁺ under different conditions, but the physics processes and plasma characteristics within the discharge chamber are not very clear until now. Langmuir probe, laser detachment, absorption spectroscopy and optical emission spectroscopy are common approaches for diagnosing the plasma. Among those methods, optical emission spectroscopy is a simple in situ one without disturbing the plasma. To better understand the plasma producing processes, a new ion source with transparent quartz discharge chamber was designed at PKU so that plasma diagnostic can be performed through directly detecting the light generated within ECR zone by fiber optics. Collisional radiative (CR) model is utilized to calculate plasma parameters like electron density ne and electron temperature Te for non-equilibrium plasma in ECR ion source. The spectroscopy diagnosis platform has been constructed, and preliminary results will be presented in this paper. *Author to whom correspondence should be addressed. Electronic mail: sxpeng@pku.edu.cn.
	Slides MOOBMH04 [2.330 MB]