Sealed Acetylene Reference Cells with Angled Windows

Specifications
Item #	GCA20	GCA50
Reference Gas	Acetylene, >99.6% Purity
Absorption Spectruma (1530 nm Band)
Cell Lengthb	20.0 ± 3.0 mm	50.0 ± 3.0 mm
Path Lengthc	14.0 ± 3.0 mm	40.0 ± 3.0 mm
Cell Outer Diameter	12.0 ± 0.2 mm	24.0 ± 0.2 mm
Cell Clear Aperture	>Ø8.0 mm	>Ø20.0 mm
Nominal Pressure	50 Torr
Pressure Tolerance	±10 Torr	±5 Torr
Stem Height	≤10 mm
Window Angle	11.0° ± 1.0°
Window Item #	WW40530	WW41050
Window Flatness	λd
Window Wedge Angle	30 ± 10 arcmin
Window Substrate	UV Fused Silicae
UVFS Transmission (Click for Plot)
Diagram (Click to View)

• Data taken from the HITRAN database for C-12 acetylene.
• Length of the center of the cell including the windows.
• Length of the center of the cell excluding the windows.
• Measured at 633 nm
• Click link for detailed specifications on the substrate.

Features

• Sealed Acetylene Cells for Frequency and Wavelength Reference
• Pair of Windows Angled at 11° to Cell Body
  • Diverts Reflections Out of Beam Path
  • Compensates Beam Shear (Offset)
• Wedged Windows Minimize Etalon Effects
• UV Fused Silica Windows Bonded to Fused Silica Cell Body
• High Transmission Across the UV, Visible, and NIR Spectral Ranges (See Table to the Right)
• Custom Design and Manufacturing Services Available (Contact Tech Sales)

Thorlabs' Sealed Acetylene Reference Cells with UV Fused Silica (UVFS) Angled Windows are fused silica cells that contain acetylene gas (C₂H₂), which has a well-defined absorption spectrum. Gas reference cells are commonly used in spectroscopic applications such as calibration of spectroscopy kits, laser wavelength locking, and calibration of wavelength meters. For a general overview of use with absorption spectroscopy, please refer to the Application tab. 

Each acetylene cell has a fused silica body with ends closed by either Ø1/2" or Ø1" UVFS wedged windows; see the table to the right for a graph of the UVFS transmission. The windows are angled to ensure that stray reflections do not re-enter the beam path. Since the two windows are angled opposite to each other, the small beam shear (translation) from the first window is compensated by an equal amount at the second window. To reduce etalon effects, the windows have a 30 arcmin wedge.  

The reference cells offered here have been heated to 800 °C under vacuum to remove contaminants prior to filling. Additionally, each cell is helium-leak tested to ensure longevity. The actual fill pressure and path length for each reference cell are measured at time of manufacture, and a summary of the test data can be downloaded by clicking on the red Docs icon () next to the Item # and entering the cell serial number under "Download Serial Item Data." A sample of these results for the GCA50 Acetylene Gas Reference Cell can be found here.

Custom reference cells can be manufactured upon request, including different cell materials, lengths, diameters, fill tube configurations, and a variety of fill gases. Please contact Tech Sales with inquiries.

SDS sheets are available and can be found by clicking on the red Docs icon () below.

Mounting Options
These cells can be mounted in our V-Clamp Mounts, which are available in standard, kinematic, or Ø1.5" post-compatible versions. Please check that the cell diameter is supported by the mount. The VBC2(/M) Post-Mountable Band Clamp can be used to mount the GCA50 reference cell without marring. If using a clamp with a clamping arm, do not overtighten.

Other Single- and Multi-Pass Cells
In addition to gas reference cells, Thorlabs offers both borosilicate and quartz vapor reference cells that contain a range of fill materials. Also available are pre-assembled compact and Herriott multipass cells for gas absorption spectroscopy applications as well as empty cells for a variety of spectroscopic applications as shown in the selection guide below.

Click to Enlarge
Each reference cell includes a serial number, which can be used to access a test report containing path length and fill pressure.

Click to Enlarge
Angled and Wedged Windows Minimize Etalon Effects

Single-Pass Cells Selection Guide
Empty Glass Cells with Borosilicate Windows	Empty Glass Cells with Textured Antireflective Windows	Empty Glass Cells with Angled Windows	Empty Glass Cells with Brewster Windows	Empty Alumina Cells with Sapphire Windows	Threaded Empty Glass Cells	Threaded Empty Stainless Steel Cells	Vapor Reference Cells	Acetylene Reference Cells	Glass Cell Heaters

The reference substance pumped into the glass cell is associated with a unique absorption spectrum that serves as its fingerprint. The contents of a reference cell can be determined via a linear absorption measurement (as depicted by the simplified schematic below). By scanning a tunable diode laser over a wavelength range and detecting light absorption with a photodetector, a series of peaks will be recorded, which is characteristic of the gas inside the cell.

In addition to acetylene reference cells, Thorlabs' line of glass cells includes: pre-filled and sealed vapor reference cells with quartz or borosilicate substrates, empty glass cells, empty glass cells with angled windows, threaded empty glass cells, and multipass cells.