Exit Slit (SLT-600)

This slit unit consists of vertical and horizontal slit mechanisms, a vacuum vessel which houses them, a water cooling system, stepper motors with linear encoders, limit (home position) switches and electrical connections including internal wiring for beam monitorng system.

The total slit size is adjustable from 500 microns to 0 microns in both vertical and horizontal directions. The actuation is such that the blade pairs move symmetrically about a central point. The slit will go to a completely closed position. Backlash does not exceed 1 micron. A flexure design featuring no mechanical backlash is used.

Micron precision
Linear encoder
Water cooling
Beam monitoring
Blades can go "past closed" without clashing (Overlapping/Zero Beam)
Blade material;
Synchrotron Application:
Tungsten (TU) 95% W, 2.5% Ni, 2.5% Cu
Tantalum (TA) ASTM-B-708 R05200

The slit has a flat bottom and is firmly attached to a horizontal plate. There are three fiduciary marks provided per slit unit. The total power at the location of the Exit Slit can be as high as 60W total for zero order irradiation and thus requires water-cooling. A common heat sink with individual blades connected to the sink through “heat bridges" is incorporated. Each pair of slit blades is motorized by a single stepper motor drive system with a linear encoder as well as end of stroke limit switches. The complete drive assembly is linear and accurate to 1 micron of slit width.

The slit blade edges are parallel and straight to within 2 degrees and they are perpendicular with the other slit to within +/- 2 mrad. The vertical slit (with edges of the blades horizontally aligned) is placed upstream and horizontal slit downstream. The offset of vertical to horizontal pairs does not exceed 5mm.

The CF 2-3/4" flange (rotatable) connects the Exit Slit unit with bellows upstream and downstream of it. CF 2-3/4" flange is also used for direct viewing of the Exit Slit's front plate. A manually-insertable phosphorus screen upstream and a
Si photodiode downstream are used. Si photodiode is soft x-ray calibrated photodiode, such as AXUV-20 from IRD (www.ird-inc.com), and used with UHV BNC connection. The design of electrical connectors permits the 10 nA leak current measurements.

The slit position has a built-in mechanical indicator providing a visual output in microns. The linear encoder generates TTL encoder pulses, it is assembled and calibrated by ADC's engineers and has a home position with a precision of 1 micron of slit width or better.

All UHV sections are vacuum tested to better than 5x10^-10 mbar and have a leak rate of less than 2x10^-10 mbar l s^-1.

An optional stand is available to mount the slit system. This stand has holes in the steel tubes so it can be easily filled with sand for added stability. Kinematic mounts on the base offer fine adjustment when lining up the slit to the beamline.

Beam Monitoring

The blades of these slits are independently, electrically isolated and have a connector and wire to enable the drain current to be measured. This is used to determine the position of the beam. The minimum DC resistance between the blade and earth is >1010 ohms.

Fiducialization

For beamline component alignment, ADC provides fiducial points on precision surfaces. Exit Slits, for example are shipped with both scribe lines at the X and Y locations of the beam center and precision holes for mounting of
tooling balls.

Finite Element Analysis

A detailed thermal/mechanical analysis is performed. A complete FEA report is available and can be provided for customer review.

High Performance, Precision Motorized Actuator (PMA-100)

The Exit Slits use this high performance motorized linear actuator. It features a precision preloaded ball screw, mounted concentric with the non-rotating output and perpendicular to the mounting surface of its rugged housing. This configuration makes it equally adept at push-only or push-pull type applications at significantly higher loads than competitive offerings. There are no reflected loads to the preloaded linear slide that provides guidance. Therefore, the accuracy potential of its micro-stepping motor and high precision linear encoder are met throughout its loading envelope. Optical switches indicate travel limits and zero position. A non-traversing tapered connection attaches to your shaft for pull-push mode, or a steel tooling ball is mounted for push-only mode. A manual knob allows sensitive touch-off zero confirmation in push mode applications.

Encoders

Numerik Jena Optical Linear Encoder
PN: LIK21-M52-WZ.

Square wave output, RS 422 with interpolation out to a 15pin D-Sub connector
Supply voltage 5V DC ±10%
High resolution and accuracy
High interpolation accuracy due to electronic offset and amplitude control

AS: monitoring signal
NAS: negated monitoring signal
Numerik Jena LIK Encoder DB15 Pin Assignment

ORDERING INSTRUCTIONS:

Exit Slits can be ordered with different options. Please use the following chart for ordering.

For example: To order an SLT-800 slit with tungsten blades, a stand, and RGA the model number would be SLT-800-TU-S-R.

NOTE: Custom/Neutron application blades are available in boron carbide, cadmium, boron nitride or a sandwich combination structure. #2: For a copy of the FEA on high heat load contact ADC.