Physical Layout of the CD Module

Click here to see illustration with dimensions.

1. Incoming beam from monochromator.

2. Magnesium fluoride polarizer/beam splitter rigorously splits the incoming beam into two linearly polarized beams each orthogonal to the other. Their angle of divergence is 3 degree, such that the two beams of light are 3.5 mm separate by the time they reach the center of the primary cell holder (position 3). The 50 kHz Hinds PEM-90 modulates each beam at 50 kHz rate. The two beams, out of phase with each other, modulate between RCP and LCP 50,000 times per second. These raw signals are passed through the sample (position 3 (or 5)) and thence to the detectors (position 6) with zero pre-collection manipulations. (Compare this with old style CDs, wherein the raw signal is decoupled and amplified through a lock-in amplifier before being detected. Hence, there is no “raw” signal with any CD other than the DSM CDs by Olis, Inc.)

3. Primary Sample Position, wherein both beams of light are employed. The default hardware includes our water jacketed cell holder which is compatible with both rectangular and cyl CD cuvettes. In addition to the default choice, jacketed for temperature regulation with circulating fluid (shown in chamber, 3a) , a Peltier version is optionally available to substitute for the water jacketed model Peltier (shown outside chamber, 3b). Other choices include, and are not limited to, a linear six-position cell changer, The LC 600™, and a six position turret (generally used in Protein Machine versions, since this more expensive choice supports use of emission readings simultaneous with CD).

4. Water lines to cuvettes 3 & 5 with drip-free, easy-snap connection/ disconnection.

5. When the default jacketed cell holder is provided (3a), it comes with a pair of 1 cm² rectangle cell holders farther down the optical path. At this secondary position, the two beams have diverged from each other sufficiently far to allow use of two rectangular cuvettes. These cuvettes can be used for absorbance, fluorescence, FDCD, and POF. These holder positions are also useful when one chooses to scan two distinct CD samples simultaneously and when one must work with a sample less than 3 mm wide.

6. Two photomultiplier tubes: UV/Vis or Vis/NIR optimized. Each PMT reads into its own amplifier circuitry and its own fast 14 bit A/D converter. The detectors are mounted at a slight angle relative to each other so that both capture the slightly diverging beams straight-on. This detector panel and its detectors exchange without tools or alignment for a second panel and detector pair which are optimized for NIR detection.

7. The port for mounting a detector for 90 degree measurements at the secondary sample position (5), useful for fluorescence, FDCD, or POF, as well as the optional mounting of a photolyzing flash source. In addition to the detector itself, optional filters, polarizers, and a scanning monochromator can be positioned here.

DSM Associated Hardware

1. Lamp
   PTI mirrored lamp housing to achieve a six-fold effective intensity in the lamp's output, achieving maximum light intensity from the 150 watt ozone producing xenon arc lamp. Cooling supplied by cooling box, below

2. Nitrogen Regulator
   Three independent channels for control of flow to lamp housing, monochromator, and sample compartment

3. Closed-Cycle Cooling Box
   An integrated closed cycle cooling system for lamp cooling which guarantees instantaneous lamp power supply shut down if cooling becomes compromised and runs lamp below ambient for long life.

4. Lamp Power Supply for 150 Watt Xe

5. 

   Electronics Box
   All external to spectrophotometer for greatest ease in diagnosing and repairing problems.

6. Computer
   Current best Pentium Microsoft Windows™ NT/2000 compatible computer with choice of LaserJet or DeskJet printer.