CARBS Accelerator System

The CARBS (Compact Automated Rutherford Backscattering Spectrometry) accelerator system is a completely automated instrument for Ion Beam Analysis (IBA), specifically Rutherford Backscattering Spectrometry (RBS) and high depth resolution RBS (HR-RBS).

NEC has designed the CARBS system to be easy to operate with a compact footprint, automatic operation and data collection, and a positive ion source that can operate for thousands of hours with no maintenance. Also, the CARBS system expands to 1.0 MV or 2.5 MV for NRA or PIXE capability.

CARBS System IBA Techniques

The CARBS system is designed for RBS and HR-RBS (optional). The versatile design allows for additional IBA techniques to be added during design or added in the future.

Ion Beam Analysis refers to a variety of accelerator techniques that mainly focus on interactions between MeV light ions (H, He) and materials. All IBA techniques are extremely sensitive and allow the detection of elements in the first micrometers of a material, or deeper. Typical IBA techniques require beam energies ranging from 0.5 MeV to 6 MeV.

Common IBA techniques include:

• RBS (Rutherford Backscattering Spectrometry)
  • Measures heavy elements in a light matrix
• ERD (Elastic Recoil Detection)
  • Measures light elements in a heavy matrix
• PIXE (Particle-Induced X-ray Emission)
  • Provides trace and minor elemental composition
• NRA (Nuclear Reaction Analysis)
  • Measures specific isotopes
• Channeling
  • Measures defects and dopant interstitial or substitutional locations in major and minor axes of crystal structures

CARBS System Features & Specifications Beam current: He+ > 100 nA Beam energy stability: < 50 eV RMS Monolayer depth resolution: down to 5 Angstroms (HR-RBS) Ranges from 0.01% for heavy elements to a few percent for light elements Compact layout: as small as 4 m x 3.5 m Long source life with minimal maintenance: Over 1,000 hours between service	IBA Applications    Radiation damage Nuclear physics Biology Material science Environmental science Art science Archaeology	Geophysics Medicine Forensics science Aerospace science Food science Anthropology And many more…
RBS Demonstration: RBS/HR-RBS analyzes the known sample, provided by customer, to demonstrate proper function of the system. The sample should have a film thickness between 10A to 50A to show angstrom-level depth resolution. Many samples can be analyzed in 5-10 minutes.

How the CARBS Accelerator System Works 

Single-Ended Accelerator 

• The key components of an NEC accelerator system are contained in the pressure vessel, often referred to as the Pelletron® or tank.
• The CARBS is a single-ended Pelletron: it has a high-voltage terminal at one end of the acceleration tube and a positive ion source inside the terminal.
• The exit of the Pelletron is at ground potential, where the ion beam emerges with an energy equivalent to the terminal voltage plus source potential.
• By using a single-ended accelerator rather than a traditional tandem accelerator, the beam stability is greatly improved from several hundred eV down to 50 eV.
  • The footprint of the Pelletron tank is approximately half of that of a tandem.

Positive Ion Source 

An NEC positive ion source is installed in the terminal of the CARBS accelerator. Using a positive ion source allows for less source maintenance due to the lack of a rubidium charge-exchange cell. The interval for replacing canals and insulators can be up to several thousand hours of run time at moderate currents.

Produces:

Hydrogen Helium Oxygen

Chlorine and more …

90-Degree Magnet 

Post acceleration, the beam passes through a 90-degree, double-focusing magnet for proper mass analysis. The beam transmission is optimized for focusing into the IBA chamber.

IBA Endstation

• The beam then enters NEC’s standard IBA endstation for analysis. The IBA endstation includes a Silicon Surface Barrier (SSB) detector for RBS analysis.
  • Additional detectors for other techniques can be added.
• The scattering chamber can accommodate up to 16 samples, 1cm x 1cm, side by side.
  • Includes:
    • Vacuum load lock
    • View port
    • Target alignment laser
    • Video camera.
  • It is electrically isolated and can be used as a Faraday cup for precise beam current measurements.
• A 5-axis sample manipulator provides X and Z motions of +/- 12.5 mm and Y motion of +/- 50 mm with resolution of 0.001 mm.
• Theta axis rotations of +/- 160° and Phi rotation is continuous, both having 0.01° resolution.
  • The control computer, which controls all five motors simultaneously, positions the samples.
• A digital current integrator is provided to measure total ion beam current and provide gate signals for all detector measurements by monitoring total ion current on the target.
• The IBA endstation computer manages the sample positioning and data acquisition.
• The control system includes software for both qualitative and quantitative analysis.
  • Including:
    • RC43 Analytical Data Collection software
    • and RUMP/SIMNRA, respectively.
  • The IBA control system will communicate with the accelerator control system for enhanced automation.

RC43 Endstation Features:

• Holds up to 16 samples side by side 5-axis target manipulator
• Can include detectors for RBS, Channeling, ERD, PIXE, PIGE, NRA, and IBIL
• Analysis computer incorporates software that allows for:
  • 6 spectra to be gathered simultaneously
  • up to 10 spectra to be plotted and overlaid with color and line styles that are automatically changed

 

HR-RBS Detector System

Users have the option to add the HR-RBS detector to the CARBS system to allow for high-resolution detection of the scattered beam. This detector provides monolayer depth profile sensitivity (~5 angstrom).

HR-RBS Features:

• Energy Resolution: 1 keV
• Accurate positioning for small-angle grazing measurements
• Designed for compatibility with RC43 endstation; however, configuration to fit with other experimental chambers is doable
• Equipped with all necessary hardware and software for automated RBS data collection and analysis
• Advantages over traditional IBA include:
  • Depth sensitivity
  • H profiling
  • Crystal quality dopant location
  • … and more

Analysis Computer

The IBA endstation computer manages the sample positioning data acquisition with qualitative and quantitative analysis. The IBA control system communicates with the accelerator control system for enhanced automation. This includes system start up, sample queue data collection, channel axis location and aligned data collection, and shut down after completed sample list. Each of the previously mentioned IBA techniques are measured simultaneously and displayed on screen.

Options

There are three versions of the CARBS, based on the terminal voltage of the Pelletron. We offer terminal voltages of 0.5 MV, 1.0 MV, and 2.5 MV. The optimal beam energy is related to the techniques of interest.

The Optimal Beam Energy for Your Technique
0.5 & 1.0 MV	2.5 MV
Primarily for high-resolution RBS and forward scattering ERD for thin samples ~1000 Angstroms.	Allows standard PIXE and ERD as well as some nuclear reactions for depth profiling of thicker samples of ~2 microns. PIXE done primarily with protons around 2.5 MeV.

For any questions regarding the CARBS System, please connect with NEC here.

 

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NEC CARBS System