TOPSHIM Automatic Shimming Precautions 

Automatic Shimming with a Solvent Height of 4cm:

Topshim is a programmed feature for automatic shimming in nuclear magnetic resonance (NMR) instruments. Optimal performance is achieved when using a solvent height of 4.0 cm (650 μl). The use of automatic shimming (Topshim) is prohibited when the sample solvent is shorter (< 3.0 cm).

When the solvent is less than 3 cm in height, Topshim will utilize higher current in the higher-order shimming coils to complete the shimming task. This results in an increase in the temperature of the shimming coil, causing a drastic change in the magnetic field. This temperature rise can ultimately lead to the gradual loss of functionality of Topshim.

Improvement Methods for Insufficient Solvent Height:(Choose one of the following)

1. Increase the solvent volume to achieve a height of 3-4 cm (requires 500 μl - 650 μl).

2. Use a Shigemi tube with a height of approximately 2.0 cm (requires 330 μl).

3. Manual shimming: Use the mouse wheel to adjust z1, z2, x, y, and other second-order shim keys in the bsmsdisp Main window. Ensure that the lock level in the lock window continually rises until it cannot go any higher.

Explanation : Manual shimming does not affect higher-order coils dramatically and avoids disturbances in the    

                        magnetic field current.

Reminders:

1. When the solvent is insufficient, ensure that the sample centerline is aligned with the probe centerline.

2. Before starting shimming, pre-load the ShimFile (rsh bbfo).

3. Prior to closing Topspin, each user must reload the ShimFile (rsh bbfo) to ensure that the current returns to normal values before exiting.

Date: 2020.04.15

TOPSHIM自動勻場 注意事項 

溶劑高度4cm 高的自動勻場 :

  Topshim 是核磁共振儀自動勻場之程式設計，自動勻場在使用 4.0 cm 高(650ul)溶劑有最佳果效，如果樣品溶劑較短(< 3.0cm)，禁止使用自動勻場(topshim)。

    當溶劑較少(如 3cm 高)時， Topshim會在高次方勻場線圈使用更大的電流來完成勻場任務，而使勻場線圈的溫度(Shim Coil Temperature)增加，升高的溫度會導致磁場變化激劇，最後使Topshim漸漸失能。

溶劑高度不足改進之法 : (須擇一而行)

1. 加足溶劑直到 3 ~ 4cm 高 (需500ul ~ 650ul )

2. 使用shigemi tube約 2.0cm高(需330ul)

3. 手動勻場 : 使用滑鼠滾輪在bsmsdisp Main頁中勻 z1, z2, x, y

    及其他2次方以下shim key，並使 lock level 在lock window

    視窗中不斷上升至不能而已。

說明 : 手動勻場不勻高次方線圈，不激劇影響磁場電流

 提醒:

 1. 溶劑不足時，樣品中心線應置於量深器中心線處

2. 勻場開始之前， 預先讀入ShimFile (rsh bbfo)

3. 每位使用者關閉Topspin之前，務必再讀入ShimFile (rsh bbfo)以確保電流回歸至正常值才離開

2020.04.15