SDD 探測器的 eMLC-1 外部准直器

用於 Amptek SDD 和 Fast SDD® 探測器的外部准直器 !!

Amptek 的 eMLC-1 外部准直器是一個附件，可用於減少 X 射線從廣角進入 Amptek SDD 和 Fast SDD® 探測器的通量，從而改善背景並減少光譜干擾。 外部准直器的效果在很大程度上取決於儀器的幾何形狀; 許多客戶都會為他們的應用設計自己的准直器。 這是一個通用工具，可在許多應用中使用，也是定製設計的基礎。

Amptek 的 SDD 和 Fast SDD® 探測器包括一個內部多層准直器（MLC），它可以防止 X 射線到達電荷收集不理想的探測器有效體積的邊緣。 eMLC-1 使用相同的多層准直器，它採用黃銅外殼，並安裝在外部。 多層准直器可以有效地阻止 X 射線，其核心為鎢，並採用逐漸降低 Z 的材料層來阻擋其特有的 X 射線 ; 外層是鋁。

應用

下面的光譜顯示了外部准直器的應用。 這些光譜是使用 Amptek 實驗人員套件和配備 W 和 Al 管濾光片的 Ag 陽極 X 射線管從高密度聚乙烯樣品測得，該樣品應不含金屬。 黑色軌跡線是在探測器上沒有外部准直器的情況下採集所得。 可見的峰包括Fe、Ni和 Cu（這裡的 Ni 來自於探測器蓋的邊緣，其它材料來自夾具）。 橙色軌跡線是在使用 eMLC-1 的情況下採集所得。 鎳強度降低了 7 倍，而其它線則完全消失。 總計數率由於立體角減小而降低了 20%。


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多層准直器（MLC）： 基底金屬為 100 μm 的鎢（W），第一層為 35 μm 的鉻（Cr），第二層為 15 μm 的鈦（Ti），最後一層為 75 μm 的鋁（Al）。
准直器外殼： 基底金屬為0.020英寸黃銅，表面鍍鎳。 請注意，這位於探測器0.010英寸鎳蓋的頂部。
開口面積： 17 mm²

幾何參數
下圖顯示了機械設計。 請注意，外殼通過外緣的梯級與鈹視窗保持在0.020英寸的距離。

External Collimator for Amptek SDD and Fast SDD® Detectors

Amptek’s eMLC-1 External Collimator is an accessory which can be used to reduce the flux of X-rays entering Amptek’s SDD and Fast SDD® detectors from wide angles, improving background and reducing spectral interferences.  The optimum external collimator depends strongly on the geometry of a particular instrument; many customers will design their own collimator for their application.  This is a general purpose tool which helps in many applications and is a basis for customization.

Amptek’s SDD and Fast SDD® detectors include an internal multilayer collimator (MLC), which prevents X-rays from reaching the edge of the detector’s active volume, where charge collection is poor.  The eMLC-1 utilizes the same multilayer collimator, mounted externally, in a brass housing.  The multilayer collimator stops X-rays efficiently, with a core of tungsten, and layers of progressively lower-Z materials to stop its characteristic X-rays; the outer layer is aluminum.

Application

The spectra below illustrate the use of the external collimator.  These were obtained from a sample of high density polyethylene, which should not have metals present, measured using Amptek’s Experimenter’s Kit with an Ag-anode X-ray tube equipped with W and Al tube filters.  The black trace was taken without an external collimator on the detector.  Visible peaks include Fe, Ni, and Cu (there is Ni from the edge of the detector cover, with the other materials in the fixture).  The orange trace was taken with the eMLC-1.  The Ni intensity is reduced by a factor of 7 while the other lines are removed entirely.  The total count rate is 20% lower due to the reduced solid angle.


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Multilayer Collimator (MLC):  The base metal is 100 µm of tungsten (W), the first layer is 35 µm of chromium (Cr), the second layer is 15 µm of titanium (Ti), and the last layer is 75 µm of aluminum (Al).
Collimator housing:  The base metal is 0.020” brass, with a nickel finish.  Note that this is on top of the 0.010” nickel cover of the detector.
Open area:  17 mm²

Geometry
The drawing below sketches the mechanical design.  Note that the housing is kept 0.020” from the Be window by the small step at the outer edge.