Magnetic Active Compensation System for Electron Microscopy

ETS-Lindgren's wideband high resolution digital Magnetic Active Compensation System (MACS/D™) provides cost-effective, maintenance-free attenuation of environmental magnetic fields adversely affecting high resolution Electron Microscopy (EM), e-beam wafer fabrication (lithography), and other charged-beam instrumentation.



ETS-Lindgren's EMF-compensating (EMFC) digital Magnetic Active Compensation System (MACS/D™) provides cost-effective, maintenance-free high performance attenuation of dynamic environmental magnetic fields for maximum performance of high resolution electron microscopy instrumentation and other sensitive charged-beam scientific and production apparatus. The MACS/D system features high resolution, ultra low latency digital processing with characteristically low intrinsic noise floor and negligible drift, permitting attainable noise level and stability of better than 1 nT (.01 mG)/hour. For special applications requiring low system noise or extended high frequency response, specialized probes and complementary signal processing options are available.

ACR technology (patent pending), incorporated in the MACS/D digital architecture, provides higher compensation than other active compensation systems in any arbitrary region of the protected volume within the system compensation coils at significant distances from the actual probe location, permitting location of the probe away from sources of high extraneous magnetic fields, such as ion pumps. Custom high-power coil drivers provide constant attenuation over a wide dynamic range that can extend to ±45 µTesla (±450 mGauss) with standard coil sets in each of the three axes. Additionally, the high efficiency, low dissipation MACS/D coil driver amplifier insures long-term system reliability at sites with frequent high-level interfering field levels.

Signal processing within the MACS/D system is accomplished entirely in the digital domain by a 450 MHz DSP engine. For ACR offset attenuation enhancement, a parametric digital processing algorithm is applied in real time to generate an offset compensating signal at the probe.

For operator convenience, the MACS/D controller front panel screen provides three-axis residual magnetic field scrolling displays, with text descriptions of instantaneous axial field values, the MACS/D system configuration, system state, time and date, and LAN IP. An embedded machine control computer provides full LAN-based capability for site setup and remote diagnostic viewing that includes real-time HTML-based monitoring displays of up to 35 parameters. Additionally, password protected access to MACS/D standard and advanced operational parameters, DSP coefficients and system configuration is included in the standard software package. VPN client support is available for secure remote data logging and diagnostics, and the VPN support ensemble also includes provision for downloading of software upgrades.

ETS-Lindgren MACS/D systems for charged beam instrumentation employ traditional negative feedback, but with wideband, high resolution state of the art signal processing entirely in the digital domain, permitting incorporation of complex filter compensation and ACR algorithms to enhance performance. Along with the flexibility of the DSP based technology, the MACS/D system provides superior compensation for higher order effects attributable to residual environmental field gradients.

MACS/D capabilities are based on fast, high-resolution DSP based signal processing and a unique control/computing architecture that provides maximum software and firmware flexibility. In addition to performance and operational advantages, the MACS/D can be either locally or remotely updated with software and DSP firmware upgrades, maximizing long-term utility. From a reputation as industry leader with over 200 high performance MACS™ EMFC installations worldwide, introduction of the MACS/D system advances ETS-Lindgren to a preeminent position of currently sourcing the world's premier active compensation system for EM and sensitive charged-beam instrumentation sites.

Key Product Information

Autonomous Operation

Even absent remote monitoring or control, the MACS/D will resume normal operation in compensation mode with most recent parametric settings after a.c. power interruptions or even in the unlikely event of a Machine Control Computer (MCC) failure. At start-up, the system performs comprehensive self-tests under MCC control to confirm hardware and software integrity. In the event of an MCC failure, the MACS/D system remains operational and the front panel displays a warning notice advising the site operator to contact system service personnel.

MCC (Linux-based Machine Control Computer).

Remote Internet access via VPN client (typically in conjunction with an ETS-Lindgren managed VPN server) provides maximum network security. The VPN client provides the ability to remotely and securely monitor, troubleshoot, repair, diagnose, and update firmware/software from any Internet access point.

Increased Power

The MACS/D system employs significantly more powerful and efficient coil drivers than previous MACS versions or any known competing active compensation system, resulting in at least 100% greater field compensation ability in each of the 3 axes, typically >15uT (150mG) for coils utilizing a single turn per axis of MACS/D standard gauge multiconductor cable installed in accordance with typical room geometry. Higher compensated magnetic field values can be attained by installing additional cable-turns and/or larger gauge cable.

Comprehensive Monitoring

The front panel LCD displays real-time field level monitoring, system status, time and date, local IP address, system configuration, and warning/error messages. In the event of MCC failure, the system continues to provide field compensation with the same parameters but an error message is presented in place of the normal readout display.

iMac2 SSD:Users:cdunnam:!   RAOUL HD:!  LINEAR:!   LRA PROJECTS:!  ETS-LINDGREN:! MACS--ALL:!   MUPD I,II (MACS-DSP Upgrade Project):!   MUPD II:170523 MEA Front Panel Display Screen Labeled.png
MACS/D-EMFC-ACR (MEA) Controller front panel display: (1a) Field Level Monitor, provides readouts and 1 minute, 1 sample/second scrolling record of averaged magnetic field absolute magnitude; (1b) System Status, displays system machine state, "OPERATE" indicates normal operative condition; (1c) Time and Date, automatically updated when accessing VPN server, maintained by local reference clock when external lookup not available; (1d) Local IP Address, DHCP or fixed, displays "No IP Address" if LAN is not connected or is inoperative; (1e) System Configuration, displays configuration in format "MxA", where "x" indicates the application, for EMFC sites the configuration is  "MEA" as shown. LAN/Remote monitoring includes independent selection of all or any subset of system readable variables (see specifications, below), updated on a 1 reading/second chart or charts.

Straightforward Setup

Setup calibration requires only straightforward adjustment of the axial output gain settings, which are room geometry and probe location dependent, and a subsequent adjustment of the ACR level parameter for each axis, if probe offset is desired in the presence of significant protected volume interfering signal gradients. These setup parameter values are stored in nonvolatile memory and are reloaded at each power-up occurrence.

Specifications Select a tab below for more information

​Input Voltage: 95 to 125V or 210 to 240 AC (50/60Hz), 15A Maximum 

Magnetic Field Sensor: ±1 mT/10 G Fuxgate Probe, Tri-axial, Plug-compatible with and Powered by System Controller
Noise Floor: <0.4 nT (4.0 µG) rms, Determined Primarily by Sensor Noise Contribution.
Baseline Acquisition Range: ±900 µT (Maximum Permissible Environmental Static Field for System with Above Probe)
Operational Range: Baseline ±99.99 µT 
Front Panel Field Display Range: 99.99 µT (Averaged, Weighted Peak Absolute Magnitude) 
Frequency Range: 0.8 mHz to 100 Hz (-3 dB); 0.5 mHz to 180 Hz (-12 dB); ACR .01 to 10 Hz 
Magnetic Field Attenuation: Factor of 70 (38 dB) Minimum, Location of Maximum Attenuation Point with Respect to Probe can be Modified by ACR, in Presence of Field Gradients. 
Remote Monitoring:
  • Residual Main X, Y, Z Axial Fields, Absolute Magnitude, 99.99 µT Maximum
  • Residual Main X, Y, Z Axial Fields, Raw Data, ±99.99 µT
  • Aux (Optional Probe) X, Y, Z Axial Fields, Absolute Magnitude, 99.99 µT Maximum
  • Aux (Optional Probe) X, Y, Z Axial Fields, Raw Data, ±99.99 µT
  • PEM (Parameter Extraction Module) X, Y, Z Coil Currents, ± 7A Maximum
  • Drive (Signal to CDA/Coil Drive Amplifier) X, Y, Z, ±10V f.s.
  • AMP CURRENT (CDA a.c. Mains Input Current), 10A rms, Maximum
  • ACR Signal Nodes Through DSP Processing Chain (Development Aid)
  • Utility I/O Channel Values (Reserved, not Currently Active) 
Width: ​​53.34 cm (21 in)
Height: 22.9 cm (9 in)
Length: 43.18 cm (17 in)
Weight: 27.22 kg (60 lb)



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Key Features

  • Remote access for all Monitor, Setup, Diagnostic and Parametric Adjustment capabilities
  • High performance, reliable DSP architecture applies advanced signal processing algorithms to achieve superior environmental shielding specifically for charged-beam instrumentation
  • Three-axis high power compensation corrects for magnetic EMI in extreme environments
  • Effective protection against fluctuations in magnetic fields caused by subways, elevators, moving vehicles and a.c. magnetic fields from electrical distribution equipment
  • Cancellation of environmental AC/DC Magnetic Interference over wide frequency range
  • Probe positional offset achieved electronically via ACR option.
  • HTML Trace page permits scrolling display of any subset or all of 35 parameters
  • Data logging screen provides detailed output of System Status and Status History as required
  • Secure VPN-protected remote access; critical parametric adjustments are password protected

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