Pepperpot Emittance Meter

Categories: Beam imaging based analysis Beam diagnostics
Manufacturer: DREEBIT GmbH
The Pepperpot Emittance Meter allows to evaluate beam parameters of particles as well as x-rays in real-time. A pepperpot-like mask separates the beam into beamlets. With an image of the beamlets taken by a CCD camera, a phase space analysis can be carried out and the beam's emittance and twiss parameters can be calculated.
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Description

The Pepperpot Emittance Meter is an imaging system which allows for detecting and evaluating beam parameters of particles as well as x-rays in real-time. The setup is mounted onto a single DN 160 CF flange with a linear motion vacuum feedthrough, two SHV high voltage feedthroughs, a glass viewport, and a camera holder. The main components of the diagnostics unit are the pepperpot-like pinhole mask, a micro channel plate (MCP) and phosphor screen assembly, a mirror, and a CCD camera. The camera, the Pepperpot power supplies, and, optionally, also the linear feedthrough can be remote controlled which is especially important in case operators do not have access to the measurement setup during charged particle beam operation.

For high-intensity beams or x-rays the imaging system can be modified according to the different requirements in these cases. For example, high-intensity beams do not demand signal amplification through an MCP system. Instead, high beam intensities may require the use of special Pepperpot mask materials or an additional shutter system with active cooling to reduce the power introduced to the Pepperpot by the incident beam. Customer-oriented solutions can be offered to find the optimal setup for a specific application.

Functional Principle

Figure 1 - pepperpot scheme

The functional principle of the system is based on the incident beam being separated into several beamlets by the Pepperpot mask. In case of low-intensity charged particle beams, the beamlets are converted to secondary electrons using the MCP and finally an optical image is produced by the phosphor screen. In this standard setup, the MCP-produced electrons are accelerated onto a phosphor screen producing visible light which can be monitored through the glass vacuum window. With the help of an analyzing and control software, the emittance and Twiss parameters of the beam can be calculated from the captured image.

 

Figure 2 - pepperpot software

 

The control software of the Pepperpot system allows to adjust the high voltage for the MCP and the phosphore screen. The voltages define the amplification factor of the system. After having adjusted the voltages, the image of the ion beamlets created by the Pepperpot can be observed in real time. With an image of the beamlets taken by the CCD camera, the emittance and Twiss parameters of the incident ion beam can be calculated using the analyzing software. The software uses the x- and y-projection of the beamlets which are fitted by multiple Gaussians for the following calculations.

Parameters

Pepperpot Parameters
beam current range 0.1 pA ... 1 nA (higher currents on request)
beam energy acceptance 10 ... 60 keV (higher energies on request)
max. detectable beam diameter 40 mm (larger diameters on request)
vertical travel min. 100 mm (other travel distances on request)
minimum mask hole diameter 50 µm
General Parameters
mounting flange DN 160 CF
height 480 mm
weight 20 kg
max. bakeout temperature 150 °C
Infrastructural Requirements
vacuum conditions during operation suitable from 1e-10 mbar up to 1e-6 mbar

Scope of Delivery

  • Pepperpot Emittance Meter incl. manual linear motion feedthrough and tailored cables
  • power supplies incl. tailored cables
  • hardware and software for computer-based remote control and data evaluation

Optional Equipment

  • remote controllable linear motion feedthrough
  • vacuum chamber with beamline connection flanges according to customer specifications

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Reference Facilities

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