DuraBeryllium^® Plus windows are Moxtek’s most robust coated beryllium x-ray window. This window has an additional thin coating of polymer “Plus” applied to the already robust DuraBeryllium window. The Plus layer is more resistant to water and other harsh chemicals. DuraBeryllium Plus windows successfully withstand continuous exposure to heated water as well as to other chemicals. A series of tests were completed on DuraBeryllium windows as seen in the test summary below. Part 1 of this application note details exposure of DuraBeryllium Plus to water, KOH, and HCl. Part 2 will be released later in 2012 and will include details of exposure of this window to other harsh chemicals.

X-ray Transmission

DuraBeryllium protective layers provide corrosive shielding as well as a hermetic barrier to the beryllium foil. These protective layers are very thin and the resulting x-ray attenuation is equivalent to about 1μm of beryllium, having little impact on x-ray transmission. See chart below.

Pressure and Thermal Cycling

To demonstrate strength of the DuraBeryllium window, Moxtek pressure and thermal cycled thirty mounted windows. All thirty mounted windows were exposed to 10,000 cycles (15psi to atmosphere). Ten of these endcaps went through an additional 10,000 cycles. All windows withstood the pressure and thermal cycling without failure. The flowchart below details the testing procedure used.

Corrosion Resistance

8μm DuraBeryllium windows are very robust when continuously exposed to water at both room temperature and at 65º C. Conversely uncoated 8 μm beryllium windows will corrode when exposed to water within days. The flowchart below details the testing procedure used.

DuraBeryllium When Exposed to Water

The table below shows the robustness of DuraBeryllium windows when exposed to water.

Pass (P) = He Leak Tight (<1 x 10-10 mbar * L/sec)

Leak Testing

~60°C H2O

Room Temperature H2O

DuraBeryllium Plus

DuraBeryllium

DuraBeryllium Plus

DuraBeryllium

Approx. Time Exposure

A0177

A0156

V311

misc

A0159

A0174

A0168

A0166

A0153

3D

4D

V3112

3 hours

P

P

P

P

P

4 hours

P

P

P

5 hours

P

P

P

10 hours

P

P

P

P

P

P

15 hours

P

P

20 hours

P

P

P

P

P

24 hours

P

P

P

2 days

P

P

P

P

P

P

P

P

P

3 days

P

P

P

4 days

P

P

P

P

P

P

P

P

P

6 days

P

P

P

P

P

7 days

P

P

P

8 days

P

P

11 days

P

P

P

P

P

P

P

P

14 days

P

P

P

P

P

18 days

P

P

P

P

P

P

P

21 days

P

P

P

P

P

1 month

P

P

P

P

P

P

P

P

P

P

P

P

2 month

P

P

P

P

P

P

P

P

P

P

P

P

3 month

P

P

P

P

P

P

P

P

P

P

P

P

4 month

P

P

P

P

P

P

P

P

P

X

Fail

P

5 month

P

P

P

P

P

P

P

P

P

P

6 month

P

P

P

P

P

P

P

P

P

P

Blank box= no data collected. X= damaged.

Visual Observation

The images below were taken four months after exposure to H2O at room temperature. As seen in the images, there was some discoloration on the window coating but all windows were leak tight.

KOH Exposure Test (Exposure = 1 week)

Under extreme KOH exposure for one week, DuraBeryllium Plus did not develop any leaks. Some visual polymer delamination was observed after 6 days. Prolonged exposure to KOH will eventually dissolve the polymer “Plus” layer.

	Leak Testing Results
	10% KOH
Time Exposure	DuraBeryllium Plus		DuraBeryllium
	A0172	A0154	no number
3 hours	P	P	P
4 hours	P	P	-
5 hours	-	-	-
6 hours	P	P	P
10 hours	P	P	-
15 hours	P	P	-
20 hours	-	-	-
24 hours	-	-	P
2 days	P	P	-
3 days	-	-	P
4 days	-	-	P
6 days	P	P
7 days	P	P

10% KOH Exposure at room temp

HCl Exposure Text (Exposure = 1 week)

HCl reacts quickly with bare beryllium and corrodes 8μm Be windows within minutes. Both DuraBeryllium Plus and DuraBeryllium add some resistance to this harsh chemical but only for a few hours, as seen in the table below.

	Leak Testing Results
	10% HCl
Time Exposure	DuraBeryllium Plus		DuraBeryllium
	A0160	A0179	misc
3 hours	F	P	F
3 hours		F

DuraBeryllium Plus and DuraBeryllium Visual image above of DuraBeryllium Plus and DuraBeryllium after exposure to HCl for ~3 hours. HCl speedily reacts under the surface of DuraBeryllium.

Conclusion

Corrosion Resistance: DuraBeryllium Plus windows demonstrate remarkable resistance to corrosion after prolonged exposure to heated water. Corrosion on DuraBeryllium Plus windows is minimal and delimitation is non-existent after continuous exposure times of over 6 months without any windows developing a leak. DuraBeryllium Plus windows are affected by exposure of HCl. This chemical will slowly dissolve the outer polymer layer but the beryllium window will still be protected by the inner DuraCoat layer. More testing will be completed at Moxtek to determine resistivity of the DuraCoat to this chemical and will be reported in a later application note. HCl reacts quickly with bare beryllium and corrodes through a 8μm Be foil within minutes. Both DuraBeryllium Plus and DuraBeryllium add some resistance to this harsh chemical but only for a few hours. X-ray Transmission: DuraCoat Plus layers are applied to all Moxtek 8μm thick DuraBeryllium Plus window. The DuraCoat Plus layers consist of very thin layers of DuraCoat and polymer. These protective layers are very thin, and have little impact on x-ray transmission.

Recommendation

DuraBeryllium and DuraBerylllium Plus windows are recommended for all applications that require 8μm thick beryllium windows.